The English dictionary recognises the word, Mittyesque, as an adjective that basically describes a daydreamer. This contribution does not come from the movies, but from James Thurber's short story, The Secret Life Of Walter Mitty.
The Ben Stiller movie is the second Hollywood film that is based on the above story, and Thurber was reportedly not happy with the first version. Given that Stiller does not take a very different approach (when compared with the first movie), one wonders if Thurber is rolling in his grave right now.