When actor Daniel Radcliffe learned he'd been cast as the title magician in Harry Potter and the Sorcerer's Stone (opening Friday), he literally cried. Marvels the chatty 12-year-old: "I was sitting in the bath and my dad came up and told me, and I just sat there for a while. And then, I just started to cry. Then, I woke up at 2 a.m. and thought it was a dream!"

The youngster — who made his big-screen debut as Geoffrey Rush's son in The Tailor of Panama — also got pretty emotional when he finally screened Potter for the first time. "Again, I was speechless, and again, I cried," he admits, then quickly adds: "But I'm not a wimp! Don't let this mislead you."

Hardly a shrinking violet, Radcliffe proved quite the setside prankster during filming. "I went to the makeup bus [where] they have these steel steps outside — and I whacked them very hard with my hand to make it seem like I'd fallen," he proudly recalls. "And I rushed [in] and started to spit up all this fake blood on the floor! If [producer] David Heymen had been in there at the time, I think he may have died."

All goofiness aside, Radcliffe knows bringing a literary icon to life is serious business. And just like Harry Potter, he's a boy who's had international fame thrust on him at an early age. "I think if it was going to change my life, it kind of would have changed it by now," scoffs the kid — who's already at work on the sequel, Harry Potter and the Chamber of Secrets. "If it has changed at all, it's been for the better."