Michelle Trachtenberg is having fun on the set of 17 Again.
Saying she refers to Zac as "Dad" on set - because Efron is, oddly enough, portraying her father - Trachtenberg added:
"Anything we did, father/daughter-wise. I'd tease him, ‘I'm older than you! You're not really my father,' while he's trying to tell me what to do."