In the second youth hostel they visit, people are watching TV. The movie they are watching is Pulp Fiction, directed by Quentin Tarantino, who is one of the producers of this film.

We see the American businessman that mistakes Paxton for another customer, hit himself in the head a few times with his gun. He actually hit himself so hard that he was bleeding for several hours.

Director Eli Roth makes a cameo as the American customer wearing a Boston Red Sox jersey in the Amsterdam coffee shop who is laughing at his friend struggling to take a hit off of a bong. Submitted by wizard_of_gore

When Paxton is about to be tortured, he begs to the man in German. Director Eli Roth decided not to add subtitles, preferring to leave what was said a mystery. The lines translate as "If you kill me, it'll destroy your life. Every time you close your eyes, you'll see me. I'll be in your nightmares every night, your whole life. I will ruin it." Submitted by wizard_of_gore

Quentin Tarantino has a cameo in the bar where Paxton finds the two girls without makeup on. He is sitting across from the girls, and nearly unrecognizable under heavy makeup.