He has a dark personality and often makes pessimistic remarks, a contrast to the other interns. This has caused him some friction and some inability to become friends with the other interns and staff. At some point, he bluntly asked to be Dr. Brennnan, something that shocked her and quickly denied. He does eventually develop a quick friendship with Hodgins, who once called him "his brother from another mother".
His thesis was on how bones scatter upon falling from high heights. He had once been on a Suicide Hotline, where he got the idea, and volunteers at a sperm bank. However, he is very successful with women, as he boasted about hitting close to 100. His skill with women was proven in an episode where he got intimate with a random girl outside the theater where the movie Avatar, which Joel Moore has a part in, was premiering.
In "The Princess and the Pear", he admitted to being a "geek" and went undercover at Imagicon, a fantasy convention for a case. His future at the Jeffersonian however, was placed in doubt after he admitted to sleeping with one of the suspects.
In "The Critic in the Cabernet", he offers to let Brennan use his "discount sperm" for the baby she decides to have. He is turned down, however, in favor of Booth. Booth is against the idea of Brennan having Fisher's children because if that were to happen, it would be like "giving birth to the spawn of Satan."
In the fourth season finale (The End in the Beginning), Fisher was re-imagined as the bitter chef at Booth and Brennan's night club.
In The Mastodon in the Room, Caroline reveals that Fisher checked himself into a clinic with a case of the "hopeless vapors", but he was re-instated in The Daredevil in the Mold, where he works to cure himself of his depression, listening to calming beach noise and drinking foul smelling tea.
He was in another institution and now lives with his mother as mentioned in 'The Twist in the Twister'.
In "The Recluse in the Recliner" he has a new therapist.
- In the episode The Gamer in the Grease, Fisher, along with Sweets, and Hodgins, camps out in a theater line to see Avatar. Joel David Moore, who plays Fisher, also played Norm in Avatar. As an in-joke, or ironic twist, Fisher misses the premiere while he's having sex in the tent as everyone else enters the theatre.
- It was mentioned in The But in the Joke that Fisher is an occasional stand-up comic who has some notoriety on the underground scene. His act is made of "raw, unfiltered honesty".
- In The Patriot in Purgatory, Fisher stated he was a senior in 2001, making his year of birth 1983 or 1984, assuming he didn't skip any grades.