He tells Britain's The Sun, "I'd never really done any acting and was completely freaking out. She came to my trailer before we shot anything and was like, 'Hey, you want to go through the lines or something, wanna talk about the scene?'
"She was incredibly famous then and didn't need to do that at all. I was sitting there going, 'Oh, yeah, ok'. I had absolutely no idea what to say about it."
Pattinson's scenes were subsequently left on the cutting room floor, but he can finally see himself on the big screen with Witherspoon - they star in new movie Water for Elephants together.