Trivia

As a "thank you" for all of the free advertising the film gave them, White Castle arranged to have collectible "Harold and Kumar" cups at all of their locations during the film's release. It marks the first time an R-rated comedy is advertised on fast food containers.

When Harold and Kumar were walking to Freakshow's house, John Cho was unaware that there was a German Shepherd in the cage next to them. When the dog barked, Cho shouted and grabbed Kal Penn. This reaction was genuine.

Kal Penn, who plays Kumar, is a vegetarian, so technicians made veggie Castles for him.

On the DVD version if you go to the Menu screen you'll see Harold and Kumar driving Harold's car. If you let it sit long enough, they'll start to complain. "Why haven't they picked one of the menu choices yet? There are only, what, four choices?" Wait awhile longer: "They STILL haven't picked? What should we do? Do you want me to take my clothes off?".

This movie relaunched the career of Neil Patrick Harris who then won the role of Barney Stinson on How I Met Your Mother. Cómo conocí a tu madre (2005).