Neil Patrick Harris gets to say his famous catchphrase from How I Met Your Mother (2005) when he is challenged to a duel by Albert: "Challenge accepted!" Neither of the writers knew that when they were writing the movie. Later, during test screenings, they didn't know why audiences were laughing.
The made-up death chant that Albert bellows is actually the 1980s song "Tarzan Boy" by Baltimora.
Stephen Foster published a song in 1864 called "If You've Only Got A Moustache". The lyrics were re-written for this movie.
Ewan McGregor: At the fair, when Albert asks why everyone is laughing at Foy's joke. McGregor was shooting another movie in the area, and was happy to cooperate.
Seth MacFarlane: [reusing Family Guy gags] During his pow-wow with the Indians, Albert says "Mila Kunis, Mila Kunis" in Native American speak. The translation below reads "fine." The same gag was used with Jabba the Hutt in It's a Trap! (2011).