Awesome, Dear Boy: Jonah Hill made only $60,000 (the lowest possible SAG-AFTRA rate) on the film; he simply wanted the opportunity to work with Martin Scorsese.
Promoted Fanboy: Which could also make him this, since Hill had established as far back as in 2010 (well before he had even earned his first Oscar nomination) that Goodfellas was his favorite film of all time.
Fake Nationality: The French Jean Dujardin as a Swiss banker. Although considering that Switzerland is a multi-cultural nation with German, French, Austrian and Italian influences, it makes sense for a French man to pass as Swiss.
A lot of scenes in the movie were improvised, notably Matthew McConaghey's humming and chest-beating, which is a ritual that the actor does to prepare for his role in real life. Scorsese saw it and decided to Throw It In!. —And have all of Stratton Oakmont do it during Belfort's non-retirement speech.
Robbie Robertson then worked with McConaghey to create "The Money Chant," which plays over the end credits.
Jon Bernthal asked the extra playing the waitress to serve his cheeseburger last to add to his frustration with the whole meeting, then improvised the whole bit with the empty ketchup bottle on the spot.
Star-Making Role: Not that she was entirely obscure beforehand, as she was very known in her native Australia, but Margot Robbie's profile was increased considerably by her appearance in this film, to the point where she was widely considered a serious candidate for the Best Supporting Actress category at the 2014 Oscars (though ultimately wasn't nominated). Nowadays, people are beginning to cite her turn as Harley Quinn from Suicide Squad (2016) as her true rise to stardom, with Wolf essentially serving as her as Brokeback Mountain was to Heath Ledger. Fortunately, she didn't have to go through Dead Artists Are Better like Ledger did.