Señor Uhl sentences Jim and his friends to detention while Queen Usurna gathers evidence of a conspiracy. Draal comes face to face with Gunmar.
Jim, Claire, Toby, Eli, Steve, Mary, and Shannon have to spend Saturday detention together, and when Señor Uhl leaves to go to the bathroom, they decide to go crazy around the school and have some fun together. But while they are having fun, Draal has been possessed by Gunmar and is plotting to attack Jim at the school. Meanwhile, Queen Usurna appears to have learned about the Trollhunters's activities involving rescuing Jim and releasing Gunmar, so she threatens to send out a warrant for his arrest.
- Kelsey Grammer as Blinky
- Anton Yelchin as Jim Lake Jr.
- Charlie Saxton as Toby Domzalski
- Lexi Medrano as Claire Nuñez
- Fred Tatasciore as AAARRRGGHH!!!/Señor Uhl
- Clancy Brown as Gunmar
- Mark Hamill as Dictatious
- Anjelica Huston as Queen Usurna
- Tom Kenny as Otto Scaarbach
- Amy Landecker as Barbara Lake
- Andrea Navedo as Mrs. Nuñez
- Cole Sand as Eli Pepperjack
- Lauren Tom as Mary Wang
- Bebe Wood as Shannon
- Matthew Waterson as Draal
- Thomas F. Wilson as Coach Lawrence
- Victor Raider-Wexler as Vendel
- Jimmie Wood as NotEnrique
- Steven Yeun as Steve Palchuk
- Why everyone was sent to detention:
- Jim, Claire, and Toby were sent for "stealing" Señor Uhl’s truck (when it was actually gnomes).
- Steve and Eli got in trouble on purpose because they thought the Trollhunters were on a mission, but later realize that they got into detention for nothing (until a possessed Draal starts attacking).
- Mary got detention for making out with a guy from the rival school, Arcadia Oaks Academy.
- Shannon got in trouble for embezzling her power as the school treasurer.
- The kids all bond and have fun together throughout the entire episode. This is an interesting turn of character development for all of them, especially since they’ve all rarely interacted with each other throughout the series up until this point.
- Title: This main plot of this episode (and the title) is a spoof of the film The Breakfast Club, which focuses on a group of high school students, each members of different cliques, who spend a Saturday in detention together and come to realize that they are all more than their respective stereotypes, while facing a strict disciplinarian.
- Instead of the usual opening, the opening also parodies The Breakfast Club, showing panning shots of Arcadia Oaks High with the characters of the episode being dropped off at school.
- Draal is sadly possessed by Gunmar in this episode.
- Jim, Toby, and Claire briefly go through character derailment when they throw things at Eli and say something rude to him, just so he won’t find out their secret (not knowing that he already does).
- In fairness, however, Eli was (as usual) being nosy and it really was none of his business.
- Goof: Uhl took the groups' cellphones, but Mary still had hers.
- However, this is because she had a backup phone (which is red with polka-dots).
- Goof: The entire sequence in the gymnasium appears to span 15 minutes, according to the clock. Realistically, the group conversation in the gym lasted less than five minutes.