Will Ferrell crashes Andy Richter's book interview in a battered Buddy the Elf costume

Andy Richter had barely settled into his chair on Jimmy Kimmel Live! Monday night before a gruff voice cut through the studio: 'Boring!' The heckler, it turned out, was Will Ferrell — sitting in the audience in a dilapidated Buddy the Elf costume, cigarette in one hand, cocktail in the other.

Richter was there to promote Elf Unwrapped: Behind the Scenes of a Modern Christmas Classic, his oral history of the making of the 2003 film, and had managed only a few minutes of conversation — including a brief exchange of Dancing With the Stars memories with Kimmel's sidekick Guillermo Rodriguez — before Ferrell's interruption derailed the segment entirely.

When Kimmel tried to reframe the moment as a surprise visit from Buddy the Elf, Ferrell shut that down immediately.

I'm not Buddy the Elf, you fopdoodle. I'm Will Ferrell from the Land of the Lost movie.— Will Ferrell

Richter, taking the charitable view, suggested Ferrell had shown up to help him sell books — a reading Ferrell rejected with equal force.

Are you high? Who even are you?— Will Ferrell

Ferrell then identified Richter not as his Elf costar but as the actor who kidnapped a senator's son in the 2004 Olsen twins film New York Minute, praising that performance warmly while remaining blank on everything else about him.

When Richter reminded Ferrell that he had actually sat for an interview for the book — Ferrell wrote its foreword — the response was withering.

Is that what that was? I thought you were some Make-A-Wish kid.— Will Ferrell

A beat later, Ferrell appeared to recover a sliver of memory about the film they made together, only to deploy it as another insult.

Wait! I remember now! You were in Elf. You played the guy who came up with bad ideas for unpopular books, and now you wrote one?— Will Ferrell

The bit closed on Richter's professional identity. Ferrell announced that the book people would really want is his own forthcoming title — My Years Sitting Next to Conan O'Brien: The Will Ferrell Story — a direct provocation aimed at Richter, who spent years as Conan O'Brien's on-air sidekick.

I spent more time sitting next to Conan than you did working on Elf.— Will Ferrell

This is not the first time Ferrell has put on a raggedy Buddy costume for a public appearance. According to the A.V. Club, he previously turned up in character at an L.A. Kings game, explaining the impulse simply: 'I get these weird ideas every now and then.' The Kimmel appearance fits a pattern the outlet describes as Ferrell's habit of bringing 'format-puncturing conceptual bits' to talk show settings — apparently including his friends' appearances, not just his own.

In the film, Richter played one of the employees of James Caan's publishing executive Walter Hobbs, spending much of Elf trying and failing to brainstorm a workable holiday children's book — the in-joke Ferrell's final jab was built on.

Why it matters — The segment is a rare case of a celebrity crashing a friend's promotional appearance to mock it, and it doubles as a showcase for the kind of sustained, character-driven improv that has made Ferrell's talk-show bits a recurring late-night event.

Reported by mashable.com, avclub.com, thewrap.com, ew.com