IMDb, the Internet's go-to source for all things movies and TV, swears they have an algorithm that determines what an actor is most known for — you know, the four films that show up at the top of everyone's IMDb profile. This mathematical formula takes into account popularity, billing, and a bunch of other factors, but that doesn't mean the results are what you'd expect. So here's the challenge: We'll give some actors and you guess which movies IMDb says is their most "known for." Easy enough, right? We'll even give you the obvious ones to get started.