Timothy is always cheerful and sensitive, but usually forgets his students' names and is taken advantage of. He has a long-running romance with the science teacher, Ms. Barch. Despite constant attempts at helping people find their emotions, he shows signs of repression and cries often.
As a teacher, he tries to get in touch with students by tapping into their emotions so that they can relate to whatever it is they are learning. He has a "team player" mentality, that is often shown in episodes where there is a field trip and students and faculty travel on school buses. When it comes to violence and gore, he often shudders and writes it off as "icky."
Mr. O'Neill primarily teaches English (at Lawndale it is called Language Arts) and also teaches an after-school course on Self Esteem, at which Daria Morgendorffer and Jane Lane meet. The Daria Diaries also have him teaching Drama (Dramatic Horizons) and present English and Language Arts as separate subjects. He is shown to be well aware of a vast swathe of classic and seminal literature, such as Canterbury Tales, War and Peace, Walden, The Dharma Bums, Breakfast of Champions, and Dante's Inferno, and uses them in his class. However, his grasp of the literature and their meaning seems suspect: in "Fair Enough", he asked the class why Tolstoy made War and Peace "so darn unpleasant" (and seemed thought-provoked when Daria joked it was so nobody would want a sequel).
Mr. O'Neill was gentle, soft spoken and ludicrously sensitive, very in touch with his emotions but incapable of controlling them. His English assignments were often ill-disguised attempts to get his students to express personal pain or experiences, and he himself would often cry in class. His ability to perform such simple tasks as remembering his own students' names was come and go at best during the first season. During the summer holidays, he ran the disastrous Okay To Cry Corral.
In Cafe Disaffecto, he said he identified with Daria's essay about "being a big misfit whom everyone hates" and The Daria Diaries have him say he identifies with Daria (see below). This implies interesting things about his childhood days. We learn more in "The Daria Diaries" when he says Daria reminds him "of myself at a young age, before I discovered Gestalt and the writings of M. Scott Peck." He doesn't specify what this means, but it comes after he says he believes Daria has deep rooted issues and is detached from people.
It's possible that the younger O'Neill had problems with loneliness. We know two other things about young O'Neill: he wanted more than anything else to join the high school gymnastics team, he tried and tried, and then didn't make the grade after all (Quinn the Brain); and he joined a fraternity at college, where he had to recite the Gettysburg Address while wearing a rainbow wig and panties that said "Tuesday" (Cafe Disaffecto).
His teaching beliefs, according to Quinn the Brain, are that any student can achieve academically if their imagination and interest are engaged, and he clearly attempts to do this - he just proves unable to pull it off. When a problem student has improved in class, he has been known to 'reward' this by displaying the student or their new work to the school... which mortifies the student in question. (Esteemsters, Quinn the Brain) He is really eager to be seen by students as their friends and not just have a teacher/student relationship. This leads to things like him inviting himself to student parties. (Groped by an Angel)
In Fair Enough, for the first and only time he snapped at a student who was acting up (Brittany Taylor) to get them to pay attention, but immediately went back to his usual style after he'd got their attention. Later, when Kevin never turned up, O'Neill showed a brief glimpse of anger in referring to him as "sabotaging our play".
When dressed as a mascot in I Loathe a Parade, he tries to physically make Daria dance along with him and continues to pester her despite her protests and unwillingness. When his identity was revealed, he merely gave a bashful "oh, my...whenever I cut loose, I always go overboard".
In Is It Fall Yet?, when confronted by Link, he stated that he truly cared about helping young people. Link's response that "you suck at it" left him very upset and frantically trying to dismiss the statement. Previously, in The F Word, he'd broken down after one of his assignments had done nothing but mess up his students, crying in front of them that "I'm a failure as a teacher, as a mentor, nay, as a human being. Don't waste another minute listening to my misguided drivel". Daria ended up convincing him otherwise, but only for part of an anti-Quinn scheme.
O'Neill suffers from an allergy to pollen, and carries an inhaler (Antisocial Climbers).
The series finale/made-for-TV movie, Is It College Yet?, featured O'Neill accidentally becoming engaged to Ms. Barch, and being coached by Mr. DeMartino on how to break off the relationship. The results are amusing.
Relations With Other Characters
On the second season episode, The Daria Hunter, Mr. O'Neill (unwittingly) began a sexual-but-not-romantic relationship with the misandrist Janet Barch, which is repeated in episodes plotted similarly to The Daria Hunter, "Fair Enough," and "Just Add Water" (and was mentioned briefly in the episode "Murder, She Snored"). The clear implication is that they engage in sexual practices that most would find unusual or disturbing. They don't appear to have done much in their relationship outside of sex. Janet's attraction to him was that "you're sensitive... but you're a male!", though when he attempted (badly) to stand up to her about the engagement in IICY?, she was intrigued and attracted by the idea of him having a backbone.
DeMartino has often found him supremely irritating, but in IICY referred to O'Neill as a friend. This may have been caused by "Is It Fall Yet?", where an elated DeMartino rediscovered why he wanted to be a teacher and thanked O'Neill for the responsibility.
O'Neill also takes a strong interest in Daria's education and well-being, whether she likes it or not. She'll be called upon to read or volunteer, given extra assignments, and in the case of The Lost Girls he sent her writing in to Val Magazine without permission. In that episode, he even calls himself her writing "mentor" - he genuinely believes he's inspiring her in her work. Daria usually responds to all this with annoyed sarcasm, frustration, and occasionally a harsh attack: quite strongly criticising him in Boxing Daria for trying to get her to tell other "outcast" kids how good Lawndale was, and reading a violent revenge fantasy in Cafe Disaffecto. When he was left a despondent, depressed wreck in The F Word, Daria didn't actually care (joking that "fortunately" her and Jane had no motivation to help him) and only went along to give him a consoling speech to get something out of him.
In "The Daria Diaries", O'Neill wrote to Helen Morgendorffer saying he took a special interest in Daria because he thought she suffered from a "serious malaise" that her sarcasm was hiding, and he admitted that Daria's sarcasm upsets him. "Sometimes, after a conversation with Daria... I ache." (A letter which might have come across much better if he had gotten her surname right.)
Helen's response in "Diaries" was to chew him out for sending her these letters, attacking his views and defending Daria's "coping mechanisms" as necessary for the working world (and had at him for misspelling Daria's name). In The Lawndale File, she referred to O'Neill as being "creepy."
- Timothy O'Neill was voiced by actor Marc Thompson, who also gave voice to Anthony DeMartino, Kevin Thompson, and Charles "Upchuck" Ruttheimer III (S1).
- The Daria Diaries were written early in the show's run. Later episodes would make it explicit that Daria does suffer from real problems that she masks with sarcasm; while his letter to Helen in "Diaries" was meant to show him being overly sensitive, it retroactively indicates that he does have some insight into Daria.
- Based on "Diaries", O'Neill teaches far more subjects than any other teacher (and more than one single teacher would realistically do on a regular basis), on top of an extracurricular workshop. We don't know why, though Ms Li's penny-pinching may be the reason.
- In a June 2008 interview with TAG, CINCGREEN said of Mr. O'Neill:
"Mr. O’Neill is a horribly self-centered man who convinces himself that he’s some sort of altruist while trying to shove his theories down the throats of his unhappy students. (Maybe that’s why O’Neill/Barch works out so well: they are both such selfish people.) They are not nice characters to write about, because I don’t have any sympathy for them."
- O'Neill is similar in a number of respects to Mr. Van Driessen, from Daria parent series Beavis and Butt-head.
- In the Latin American dubbing, he was voiced by Herman López.
- In writing Legion of Lawndale Heroes, Brother Grimace (who has states that he always considered Mr. O'Neill the least worthwhile character in the series) specifically wrote in a cataclysmic mental breakdown for O'Neill, simply so that he wouldn't have to use the character anymore. Also, while writing The Winters of Those Gone Before, he had added a subplot (but later discarded) with O'Neill ending up killed by Anthony DeMartino and Janet Barch, who acted to protect Daria and Quinn so that they could get the therapy and assistance they needed.
- In the Blood Oath of Patriots series by Galen Hardesty, O'Neill's political affiliation is revealed to be 'American Marxist'. This is also used in 'Winters', when Anthony DeMartino refers to O'Neill as 'comrade' while threatening him not to bother either Daria or Jane.
- In Just Desserts by The Angst Guy, O'Neill was given a suprisingly dangerous side after he started to take direct action against people like Ken Edwards.