Pulpier films tend to get away with this better than most; often there are delights to be found in talented actors taking it easy and just having fun with a role, while it's "worthier" films that tend to be mocked for an actor's misappropriated performance. At its best, it can elevate a film's entertainment factor, and at its worst, it can make it impossible to take a film seriously.
Here are 10 awesome examples of overacting...
Gary Oldman is a supremely talented actor who finally got a long-overdue Oscar nomination last year for Tinker Tailor Soldier Spy. However, my favourite Oldman performance - perhaps even more so than his work as Jim Gordon in the Dark Knight trilogy - is as the psychotic corrupt cop Stansfield in Luc Besson's thrilling action flick Leon. This is Oldman at his most unrestrained, let off the chain by Besson and seemingly encouraged to do whatever he wants.
He delivers his character's manic dialogue ("I like these calm little moments before the storm. It reminds me of Beethoven") with nutty aplomb, while demonstrating the extent of his character's psychosis and drug addiction by jutting his jaw out and cranking his neck backwards. The most famously over-acted scene occurs during the fantastic exchange with Benny above. It's one I frequently quote with friends in the pub (much to the annoyance of bar staff everywhere I go, no doubt).