Will Ferrell poked fun at Kristen Stewart's cheating scandal Thursday. (WENN)

Funnyman Will Ferrell played into the Kristen Stewart/Robert Pattinson split drama during a late-night TV appearance in America on Thursday by sobbing about the shock break-up.

Pretending to be deeply affected by the actress' cheating scandal, the Old School star hit talk show Conan deeply depressed and began to weep as he explained why he was so low, joking, "I don't know if I could have done something to prevent it."

His upset turned to anger when host Conan O'Brien suggested, "I'm sure it's gonna be fine.”

Ferrell raged, "It's not gonna be fine, ever... What they had was so special; you would never know... She is a trampire, that's what she is."

Earlier this week, Stewart's producer pal Giovanni Agnelli jumped to the actress' defence amid the fallout following her cheating confessions, and urged critics to stop calling her a "trampire" – a reference to her vampire role in the Twilight franchise.

He tweeted, "If you've ever used the word Trampire you're a mindless pathetic piece of s---."

Stewart stunned fans and Hollywood insiders last month when she revealed a tabloid story about a fling with director Rupert Sanders was true. It now appears her romance with Robert Pattinson is over after removal vans were spotted outside the Los Angeles home the couple shares.