Dragon Ball Z Kai Episode 77

Goku: Yeah, probably at first... (giggles then walks to Gohan) Gohan, listen: once you've turned Super Saiyan, it's really gonna speed things up. Just imagine how much harder you'll be able to push me as my sparring partner... eh? Trust me. You can do it. You've just gotta believe in yourself, okay?

Gohan: Kay, dad!

Goku: Great. So, we've got a year to train, and I'm gonna find a way to go beyond Super Saiyan. I'm gonna make myself even stronger than Vegeta or Cell. As for you, by the time we're done, you're going to be even stronger than I am.

Vegeta: That was it? Really?

(Trunks looks at Cell)

Cell: (gets up) You've mocked me for the last time, Vegeta! From now on, there's no holding back!

Vegeta: Oh, so you've been holding back. Is that the problem? Well, do your worst then! I doubt it'll make a difference!

(Cell starts laughing, then powers up)