According to Hollywood Reporter (27 April 2008 issue), Warner Bros' distribution president Dan Fellman said this movie was originally produced as a straight-to-video movie until a decision was made to release it theatrically.
In an April 24 2008 Newark Star Ledger interview, the writers Jon Hurwitz and Hayden Schlossberg mention that Kumar's poem "The Square Root of Three" (parody of Joyce Kilmer's Trees) was written by a classmate of theirs, David Feinberg when all three went to Randolph High School in New Jersey. They were happy they could include in the film a poem they loved while growing up, and Feinberg was thrilled to make a contribution to the film.
Christopher Meloni, who plays the Grand Wizard in this film (the red-hooded KKK leader), plays Freakshow in Harold & Kumar Go to White Castle (2004).
The mask Harold pulls out of Neil Patrick Harris' bag is the same as the one worn by Chris Fehn from the band Slipknot.
The screenplay for this film was featured in the 2006 Blacklist; a list of the "most liked" unmade scripts of the year.
Jon Hurwitz, Hayden Schlossberg: The writers/directors play the men in the devil and monkey costumes whom the girls mistake for Harold and Kumar in the post-credit scene.