To promote Charlie Brooker's Screenwipe on BBC Four, the man himself invaded BBC Four's idents in 2007 and managed to do a variety of things. He annoyed the announcer to give her a taste of her own medicine, placed himself on top of a mountain, lazily recreated the Birds ident with a plastic seagull and a fake BBC Four logo, and BECAME the announcer himself (would you believe).
I do wonder why people don't talk about this more often, but hey ho, can't say no to anything involving Charlie Brooker.
Credit to D&AD for the footage (www.dandad.org/awards/profess...)