How James turned an argument into asking Regulus out:

James: I can’t do that. But what I can do is take you out to dinner tomorrow night.

Regulus: How do those two thoughts even coincide?

James: You’d have to be in my head but trust me there was a track.

Regulus: I am not having dinner with you.

James: Why not?

Regulus: Because.

James: Because… your mother would hate it.

Regulus: Yes, my mother would hate it!

Regulus, realizing what he said: …a lot…

James: *grinning, knowing he won*

Regulus: You suck.