Sometimes actors make good movies and sometimes they make bad movies. And most of the time they know which their current project is. Acting is, at the end of the day, a job and if it's a choice between running out of cocaine or starring in a comedy totally devoid of laughs you know what any A-List star would do. Robert De Niro, who has firmly put his past as an acclaimed actor behind him, surely must be under no illusions that the likes of The Family or Last Vegas are vapid comedies no one wants. This is the guy who played Vito Corleone (young vintage), Jake LaMotta and Jimmy Conway. He's better than the past decade of his filmography and he must know that; no one takes a career nose-dive like that without putting money well and truly first. Some actors, however, flat-out think they're in good films when the truth is the total opposite. Oblivious to the terrible direction and weak script, they're convinced this next role will be part of a masterpiece. To a degree it's understandable - gauging how the finished product will be from a screenplay is very tricky - but you'd think at some point it'd click they had a dud on their hands. Part of an actor's contract involves appearances at the press junkets before release, with some clause banning them from saying anything negative about the film. Sometimes more prominent or world-weary actors will break it (see Bruce Willis), but most of the time people are restricted from actually airing their own thoughts about a film until long after the DVD release. Even with this obligation in mind, some actors go above and beyond to appear completely deluded to what makes a good film. Here are ten such stars.