"No way! It was my idea." So there's no way he can turn around and change his mind now. He's committed, even more so with Inigo conceding despite every apparent bone in his body wanting to do the opposite. Look at that strength! Tidus has to support it!!

"I'll look up some movies later - after training. We can watch some then." Is he sure there's dance movies? Not completely, but given the library both that car and the music car has, it doesn't seem unlikely.

"But for now, I wanna see you dance!" A pause. "Or...you know. Have you dance. Behind me."

This is the part where he should be turning around, right? Tidus is taking looks and moves like he might, but there's a reluctance. But look, look, he'll be a good boy and face the other way eventually...!