One of the lies Adrian tells Mary is that Kumar works at the White House. Kal Penn, who plays Kumar, had actually been working at the White House and took time off from that job to make this movie.
When Adrian is tying the Christmas tree to the roof of his vehicle he says "let's drop this tree off at Sulu's," referring to Harold (John Cho). John Cho played Sulu in the reboot Star Trek (2009), and again in Star Trek Into Darkness (2013).
David Burtka, who plays "David Burtka" is Neil Patrick Harris's husband in their real lives. In the same way that the character that Neil Patrick Harris plays is distinguished in the credits from being himself, Burtka is credited as "David Burtka" instead of "himself." The two met on the set of the television sitcom Harris was working on at the time, How I Met Your Mother (2005).
At one point in the film, Kumar gets into a debate with someone over whether The Karate Kid (1984)] is better than its 2010 remake The Karate Kid (2010). Film cowriters Hayden Schlossberg and Jon Hurwitz would go on to write and direct the Karate Kid spinoff series Cobra Kai (2018).
Todd Strauss-Schulson: in the montage of Sergei Katsov's brutal deeds. Schulson has his throat slit by Katsov.