Lou Zarr, or Mr. Zarr is a 2010-introduced and fiction-only character. He is a human and a teacher at Monster High. His main class is Dragonometry, but he also hosts Trigular Calcometry instead of Headless Headmistress Bloodgood at times. Zarr is the only human teacher at Monster High with no ties to the monster world other than his job and it shows in the way he treats the students. He expects uniformity and respect, even though the former is impossible in an all-monster school and the latter difficult if the former is enforced. Zarr is not quick to learn from his mistakes. He is probably not the only human at Monster High, because Mr. Hackington and Coach Igor are possibly humans; and if he is the sole human, Zarr cannot tolerate it because he seems to not like monsters, according to the webisode "Substitute Creature".
Lou Zarr is the first and only teacher in the Monster High cartoon to be released a first name, but not in the entire franchise or series, due to Sue Nami and Sylphia Flapper. Which, the one, like him, also have "pun-based" or "pun-related" names. Another character in the series to be released with a first name is "Sid Borg", a cyborg, and play on the word "cyborg" itself, whose name "Sid" was not "Cy" for "Cy Borg" in the series properly because of the character, cyclops, named Cy Clops.
He is voiced by Troy Baker in English.
Lou Zarr is a stiff and humorless man who occasionally teaches Trigular Calcometry at Monster High. He demands respect from his students, but both his uncompromising attitude and name, which sounds like "loser", only bring about mockery. His methods of education aren't much better: Lou Zarr's lessons are so boring that his way of teaching even puts himself to sleep.
It may be he is not very fond of monsters or teenagers (or either), as he has referred to his students as "little freaks".
Lou Zarr takes over Trigular Calcometry 101 from Headless Headmistress Bloodgood. His demeaning attitude towards the students and intent to do the whole book don't earn him any friends. When Deuce Gorgon enters the classroom late, Lou Zarr insists that he take off his sunglasses. Deuce complies and thus petrifies Zarr. While the other students dismiss themselves, Deuce stays behind a little longer to inform Mr. Zarr that the effect wears off after a few hours... usually.
Lou Zarr hosts Trigular Calcometry 101, Frankie Stein's very first class. It makes her worry she won't survive school. In fact, Zarr's lesson is so boring he makes himself fall asleep mid-calculation. When a little later the school bell rings, the students leave swiftly, except for Ghoulia Yelps. She stays to finish Mr. Zarr's calculations; Zarr only waking up in confusion after she has completed the task.