DeMartino has a low frustration tolerance that manifests itself in his quickness to anger, his fierce emphasis of every third word, and the bulging of his left eye. Presumably this is brought on by years of trying to impart knowledge to the idiots who go to school at Lawndale, particularly Kevin Thompson.

Seemingly a glutton for punishment, DeMartino consistently calls on his dumber students to answer questions, then usually turns to Daria or Jodie for the correct answer. Despite outward appearances, he actually enjoys teaching and takes a certain pride in his work, although he takes every possible chance to cast disdain on the profession as a whole. He has indicated that he drinks heavily and regrets not having joined the Navy.

There are definitely some stories to be told in DeMartino's past. He once lived the beatnik lifestyle (according to The Daria Diaries). He is about the right age to have serve in Viet Nam, but it is unknown whether he actually did. He also had a "buddy" who married his mother - juicy details unknown. He enjoys listening to the music of Annette Funicello.

DeMartino once had a severe gambling addiction that he has never completely gotten over. He once gambled away his car, presumably among other things. O'Neill tried on one occasion to help him, but didn't quite succeed. Considering DeMartino's tendency to complain about how little money he makes as a teacher, one wonders how he ever managed to finance a gambling habit - particularly since Murphy's Law tends to apply in extra measure to him. He tends to hoard food from whatever source he can, with the result that Ms. Li has a judge's order saying he can no longer eat at school functions (he tried to load leftovers from a bake sale into his car once).

During one summer, DeMartino volunteered as a counselor for O'Neill's "OK to Cry Corral" day camp. At first he despaired of his ability to relate to young kids, but later proved very adept at it. O'Neill's policy of keeping everyone indoors for safety's sake finally got to him, however, and in a desperate bid to escape, he ripped a sink from the wall and chucked it through a plate-glass window. The kids all thought he was the greatest, and it restored DeMartino's desire to teach.

Despite their lack of anything in common aside from their profession, DeMartino and O'Neill are friends outside the school. DeMartino counsels O'Neill on the occasion that he accidentally finds himself engaged to Ms. Barch, whom DeMartino refers to as "The She-Devil who walks among us".

DeMartino is the head of the Lawndale Teacher's Union.

He views himself as a born loser, and complains that nothing in his whole miserable existence has ever worked out. Where he gets the energy to continue on is anyone's guess.

See also:  Metalmouth