Yeah, right! That hurt in Tidus's tone isn't going to fool him as long as he's still smiling!

Granted, that very same smile should be Inigo's clue that the other is joking about all of this in the first place.. And yet his mind can't reach that far, apparently. Just barely far enough to realise Tidus is not actually hurt at Inigo's refusal to let him date his sister.

"What would you do for her then, huh? You don't even know anything about her! You have no idea what she's like, so why are you interested!" He sounds defensive, but in an oddly childish kind of way - he kind of sound like he's an eight year old.

Or maybe that's just due to the way he's starting to huffily puff up his cheeks like a pufferfish.