The Joren Van Der Sloot joke had a few layers.

S6E13 "Grandmentor"

PETE: Liz, we have a show in four hours. Have you still not picked a contest winner?
LIZ: Ugh! Fine, I'll just pick one at random. It's... Joren Van Der Sloot.
PETE: We can't fly someone from Peru now! There's no time!

On the surface, it just seems like a silly joke. But the more layers you peel back tells deeper jokes.

• that name sounds silly to Americans, like a goofy name that was made up for the joke
• that name is certainly not someone you would expect to be in Peru
• that is actually a real person who was in the news recently for killing someone while on vacation or something. Pete recognizes that this is someone who is currently sitting in a Peruvian jail or whatever
• Pete doesn't care about having a murderer on the show. All he cares about is the logistics of actually getting them onstage. If it were possible, he wouldn't mind doing it.