Rotter/cartoon

Rotter debuted in the cartoon series in the Volume 1 webisode "Idol Threat", which premiered on December 16, 2010. He is voiced by Yuri Lowenthal and Cam Clarke in the English version of the cartoon.

Webisodes
Cleo de Nile considers a B+ too low for the quality of her work she did for Mr. Rotter's class, but Rotter retorts that he nevers gives A's. In order to get her rightful A from him, Cleo uses an idol with persuading powers on him with positive results.

Webisodes
During the events of "Fear the Book", Rotter was manipulated and tracked by Toralei Stripe to various location where she arranged for the Fear Squad to do something suspicious. As such, Rotter saw Cleo de Nile among a stash of balloons, noticed Clawdeen Wolf had rotten gargoyle eggs in her bag, and overheard Frankie Stein and Draculaura talking about a recipe for stinkbombs. Naturally, he believed they were preparing a prank, something he could not let go unpunished; exactly as Toralei had planned. However, the Fear Squad was aware of Toralei's hand in the situation and in "Desperate Hours" prevented the stinkbomb to be dropped during the graduation ceremony that Mr. Rotter presided. To get back at the werecats, Ghoulia Yelps gave them extra math credits so Rotter would send them off to math camp the entire summer.

Rotter tried to start his class in "Back-to-Ghoul", but got hit by a snowball thrown by Frankie Stein in a fight with Abbey Bominable. He sent them both to Headless Headmistress Bloodgood's office.

In "Ghostly Gossip", Rotter was looking over his students' test results.

TV special
After Dead Languages, Frankie Stein and Draculaura talk about how all the languages Rotter teaches sound alike, which Draculaura follows up with a mocking imitation of their teacher. Mr. Rotter notices, but assumes she's trying to replicate today's lesson and so gives her the advice to let her 'R's roll.

Volume 3
Rotter functioned as referee during the casketball game between Monster High and the West Valley Mages in "Super Fan".

Mr. Rotter helped organize the class trip to Monte Scarlo in "Uncommon Cold". Just before departure, he heard Frankie Stein sneeze and told her that she wasn't allowed to come along if she was sick.