Cena plays the actress' sexually-confused beefcake boyfriend Steven in new film Trainwreck and she admits she had no idea her love interest would be so hilarious.

She explains, "Trust me, this one was the least romantic, the least sexual of any sex scene I've ever done, simply because John was so hilarious ad-libbing those lines to me, forced to talk dirty.

"He made me laugh so much, my make-up kept coming off, I was crying so hard from laughter."

And he wasn't the only co-star who made the funny lady laugh uncontrollably - basketball icon and movie newcomer LeBron James was hilarious in his scenes with Bill Hader, who plays his knee surgeon in the film.

Schumer adds, "The scenes where he's splitting the lunch cheque and showing how cheap he is - despite making zillions of dollars - I think are some of the funniest moments in the movie."