The 28-year-old actor asks his Dirty Grandpa co-star to wish his girlfriend Sami Miro a happy birthday.
When a simple “happy birthday” doesn’t satisfy Zac, he asks Bob to hold balloons, sing, and give more energy.
It doesn’t go so well. Watch Bob tell them off in the video below!
“Oh my God, you better love that,” Zac tells her.
Zac Efron & Robert De Niro – Funny or Die Video