Troy just forgets that he's speaking sometimes, it's like words are coming out and he's not even listening to himself, so he'd apologize for a) calling her sister hot, and b) mentioning Dawn was equally hot if he'd even realized he'd rambled about it in the first place, but he's already forgotten about it. Maybe he'll redeem himself later.
".. Of me?" Aw, look at him go all bashful and awkward as he squints shyly and stuffs his hands into his pockets, shoulders hunched and ball tucked under an arm. "Eeh. I'm not. I mean, that's just. I'm just a normal guy. That's got to be the most boring movie ever. There's not even like, vampire slaying or demons or anything cool."