In the real world, Sid, Manny, Ellie, and Peaches travel to Tokyo where they help explain to the citizens about how important sloths and woolly mammoths have been during the ice age, including themselves.

"Oh, it's so nice meeting you all. We've never seen animals like these before at all." A woman kindly interacts with Sid and the three mammoths. "Animals such as you four don't exist in this country, but just seeing you for the first time is worth a memory in the future."

"That is why we came from our universe into this world so we could help everyone understand in Tokyo learn about species from the ice age era!" Sid gladly shakes his hand with the woman, who is really taking a like at him.

Manny begins the introduction for the humans, saying, "The name's Manny, and these two are my wife Ellie and my daughter Peaches. The three of us are woolly mammoths and Sid is my friend, and he's a sloth. These three have been important to me and we thought we all come to the real world and see you humans again, knowing how life has changed since. Me and Sid have known humans back in the old days, but Ellie and Peaches don't, so I decided to take them on my journey and tell them about you humans."

Peaches walks towards the woman holding her oil-paper umbrella, also known as the 'Wagasa'. "Knowing that I'm not familiar with humans as my father, it's an honor meeting you humans for the first time." Peaches said, interacting with humans for the first time.

"And this whole world has more humans than the ones from our universe. There aren't any humans in our world." Ellie told the unnamed Japanese woman.

"I understand. I respect your feelings." The woman replied, putting her right hand on Ellie's cheek and understand her emotions.

"Isn't that so adorable?" Sid asks Manny, watching the woman showing her opinions about Ellie and Peaches caring for humans in the same manner Manny has had himself a long time ago.

After hugging Peaches and Ellie respectively, she hugs Manny and Sid and she waves goodbye to them all before leaving, allowing the group to continue their journey in Tokyo.

As the group continue walking throughout the city, Sid can spot the Tokyo Tower from nearby, and he and the others take a look at it briefly before they resume strolling through the streets. Sid was really excited about visiting Tokyo.

"That lady was nice, I can say that much." Sid tells the three mammoths, who all nod in an agreement that humans seem very nice and polite towards them.

"I do gotta get some earrings for my wife. She needs them to make her look more beautiful when we head back." Manny thought about buying some earrings for Ellie, since mammoths never worn any accessory.

Ellie declined the offer saying, "Honey, I'm already beautiful as is. Earrings can't fit me because of my size."

"That's great and all, but um, you guys don't realize that we forgot to bring Shira and Diego with us." Peaches reminds the group that they have not taken the Saber-toothed tigers along with them for the adventure in Tokyo.

"Uh oh, looks like those two must be missing out on the fun!" Sid looks disappointed that he is missing Diego and his wife Shira, too. "Man, they have to be around here somewhere..."

"And where are those two anyway?" Manny was beginning to wonder where his saber-toothed tiger friends have wandered off into.

"That's what I'm thinking of as well. They can't just have disappeared like that." Ellie said.

While the group feels unsure about where Diego and Shira have been, they end up hearing screams and shouts from several tinies, who ran past them as they are running away from something huge and deemed threatening, leaving them group confused.

"Run for your lives, everybody! There's two gigantic tigers invading Tokyo! They'll find you and they'll crush you!" One man warned that there's two giant saber-toothed tigers spotted and are somewhere approaching even more closer than anyone would think right now.

"Is he talking about...?" Ellie asked Sid, Manny and Peaches nervously before her question got interrupted when she and the gang just heard an extreme, thunderous step to the ground.

The group knew that they were right. Shira and Diego have been somewhere in Tokyo, and now Manny and gang realize that Shira and Diego are the ones who are stomping their way through the city, crushing and flattening vehicles, objects and building below their massive paws. All eight paws together would shake the whole planet.

Manny notices that Shira and Diego are both huge, even bigger than the whole city itself, as well as the Tokyo Tower. The more times the giant tigers keep on strolling, the louder the sounds will get, and it was definitely like an earthquake for sure.

Diego walked past the tower as he sent his front right paw to the ground, shaking the ground even further.

"My, let's take a seat here, shall we, my love?" Diego asks Shira with a grin on his face.

"Oh, we should. Definitely should sit on these buildings and crush them until they are flat as a pancake." Shira agrees and she and Diego sit down and flatten the buildings underneath them, causing the ground to shake as twice as hard.

Peaches, Manny, Ellie and Sid all react in shock over how big Diego and Shira are. It was more than enough for Manny to realize that Shira and Diego are much more heavier than him, in both size and weight.

"They're HUUUUUUUUGE!!!" Peaches said with a surprised expression.

"And perhaps dangerous." Ellie commented on how powerful Shira and Diego would be, seeing the two as a possible threat to Tokyo.

Back with the two massive-sized saber-toothed tigers, Shira starts flirting with Diego in an unusual manner. She looks at him in awe, as she knows that is he most important one that she has cared for the most out of anyone.

"Drinking that growth potion really was worth imagining what would happen if we were to become the biggest animals in the entire world." Shira told Diego, having recalled from earlier that the potion she and Diego drank would take an effect on the both of them in a big way, much to their satisfaction.

"Having deep voices, stronger strength and power, we got powerful claws that hurt a hundred times to everything and everyone." Diego chuckles, being so proud of himself with pride that he feels like he deserves to be bigger than everyone, including Sid and Manny.

"Nothing can stop us as long as we stay giants!" Shira laughs, knowing she and her husband can't be touched, no matter what happens, and she thinks she will remain a giant forever.

"What do you say we go stomp through this city straightforward?" Diego asked Shira, putting himself in a mood to start having fun and cause some destruction.

Shira giggles with a smug smirk on her face, replying, "I like the sound of that!"

Both giant-sized tigers get up, standing on all four legs again. Because Shira and Diego are absolutely large, their movement speed decreases whenever they walk and run. They raise their paws up and then bring it back down to the ground with a powerful stomp, shaking the city, with every print shaped like paws being left on the ground.

As Diego and Shira proceed to move on, Manny, Sid, Ellie and Peaches all come to an agreement that they must stop Diego and Shira from destroying Tokyo any more from the destruction they have already caused at this point.

However, the group realize that the only to do this is to find the scientist who had a shrink ray, hoping the enormous saber-toothed tiger duo can return to their regular sizes.

"If we don't find the scientist who can shrink those two, we and this city are in big trouble!" Manny warned the group that they must do something to prevent the giants from tearing up Tokyo.

"We better act fast, dad, because time is ticking, and we have to find the man who has a thing that can get Diego and Shira back to normal!" Peaches said as she and her parents, along with Sid, all search for the man that has at least a shrink ray gun that can bring the saber-toothed tigers into the size they were before now.

Elsewhere in Tokyo, people are running from the giant saber-toothed tigers as they approach with heavy paw steps that shook the ground even just as thunderous as the previous one.

"Get back here, you speedy little devils!" Diego raises his voice as he spots the tinies down below on the streets, chasing the tinies who are in his sights. He stomps on a vehicle and when his back left paw came off the floor, he left the crunched car on the ground.

"These magnificent humans will be ours! There's not anything or anyone who can tell us what to do now!" Shira cackles loudly, her voice echoes and shatters windows inside buildings.

"Tigers rule the world, and we're large in large and in charge, meaning Tokyo will be ruled by me and my beloved Shira! Time for some fun!" Diego told his lover, who agreed with him as they decide to stomp their way through the city together and do anything as they wish.

Shira and Diego let out a roar so loudly, it is making hard for everyone to try and cover their ears. They knock over and stomp on buildings in their path, damaging and destroying them.

A man inside his red truck was silently listening to the news about the saber-toothed tigers roaming and attacking Tokyo. Unfortunately, the radio was soon cut off, and he unsuccessfully tried to turn it back on. He then hears screams and shouting from other people outside.

He gets out of his truck and discover what's happening. He watches the people in front of him flee in terror from the two giant tigers Shira and Diego. In fact, while facing forward, he soon sees the huge shadows of the massive saber-toothed tigers cover him in the darkness.

With more booming sounds coming from the two large tigers, they come closer and closer and the man screams and dodges out the way in time just as Diego lowers his enormous front right paw straight on down to the truck he owns, destroying it. He looks up in shock, knowing he can't do anything to stop them.

Nevertheless, Sid, Manny, Ellie and Peaches all have returned with a scientist named Dr. Suzuki, who is holding a shrinking ray gun. They look at the man, who felt hopeless.

"Hey, what's going on here?" Dr. Suzuki asks the man, wondering what the situation is.

"There were two giant monsters that just walked right past me, and one of them just flattened my truck into nothing but junk!" The man explained with a panicking expression, and he almost wanted to cry that badly.

"Are you talking about Shira and Diego?" Sid questions the man, wondering if he was talking about them.

The man nods his head and replies, "Yes, those two."

Manny orders his group to start moving, and before they do so, he appreciates the man for telling them where Diego and Shira are, deciding they must hurry and catch up to them before it's too late.

As the enormous saber-toothed tigers both walk slowly due to their size, Manny, Sid, Ellie, Peaches and Dr. Suzuki are manage to quickly run on the feet and stop the two from wreaking Tokyo and they are almost close to getting on their tails.

"Hey, you two, stop it now!" Ellie yelled, ordering Diego and Shira to stop walking and try and listen to her and her friends.

However, both Shira and Diego didn't hear Ellie or anyone else due to them being too small and they still kept on walking, shaking the ground more loudly than before.

No choice but to put their plan into, Dr. Suzuki allows Sid using his shrink ray gun and aim at both the saber-toothed tigers and shrink them one at a time. Sid was excited doing the honors and he shrunk Shira first while she wasn't noticing him.

When Diego reacts in confusion after seeing Shira reverting back to her normal size, he looks back and discovers that Sid was the one who did. This angers Diego, who threatens to scratch Sid with his claws in case the latter doesn't stay out of the way.

"How dare you do that to my Shira!" Diego shouts at Sid, berating him for shrinking Shira.

"Relax, now, tiger, we gotta put you in control before you mess up Tokyo more, buddy!" Sid presses the button on the shrink ray gun again, shrinking Diego next and he reverts back to his normal size as well.

Though the two look so exhausted after learning that they can't giants forever, Shira and Diego more likely are disappointed in them and regret with guilt, knowing they shouldn't have drank the growth potions in the first place.

While Diego was looking more silent, Shira has given Dr. Suzuki an apology, saying, "We are so sorry for drinking your growth potions without asking you. We knew that it would take a turn for the worse, and that it would make us become giants and we just didn't had any control of ourselves and attacked the city."

"Yeah, I guess we got kinda carried away." Diego adds on further to what Shira explains. "I think we are so sorry for being very rough against these people..."

Dr. Suzuki still hugs Diego and Shira one at a time and he accepts their apology.

"Well, at least we just solved the problem and save the day." Dr. Suzuki told the group, seeing that they all make a difference to all of society. "If it wasn't for me, I'd probably end up being in trouble. Big trouble!"

"I'm so happy you two are back to the sizes you are now!" Sid hugs Shira, making him the second person to do so. Shira blushes nervously at Diego, feeling guilt inside her.

"Don't feel sad, my love. Everything is gonna be okay." Diego comforts Shira, telling her that the situation is over and that they are no longer giants.

Shira was coming to her senses and found herself more relaxing and happy.

"Now we better get going and get out of here." Manny told the group, as he led his group back into their own universe, hoping that no more troubles can happen later on.

Sid waves goodbye at Dr. Suzuki as the latter smiles at him and his saber-toothed tiger and woolly mammoth friends for showing some kindness and respect in the end. Sid admits that he still loves Diego and Shira, no matter how big or small they are.