Starting off with Alan cuz he's my favorite character.
1) A lot of people I've interacted with say he's possibly autistic or has OCD, while these are all really great possibilities, I'm kind of on the fence with this one. Will probably wait until after the special before I make any further judgments.
2) He wishes to have a job similar to Charlie and Pim's that involves helping clients, so he tries to focus on the most simple of tasks.
3) This is kind of connected to what I just mentioned, but Alan often feels that if he doesn't do anything productive, he'll be considered a failure among his boss and other fellow co workers.
4) DEFINITELY a perfectionist in every sense of the word.
5) fluffy....
6) Alan is more reserved, which is why he hasn't been seen interacting with the other critters all that much.
7) Outside of work, he thinks about a lot of deep topics that would take you aback if he were to talk about them.
8) Is very weary of friendships or relationships. Due to a lot of difficult circumstances, Alan prefers to not associate himself in any real relationship minus what he has with Charlie, Pim etc.
9) After the events of the pilot, he's developed a traumatic fear of bliblies. This goes as far as to having vivid nightmares of the incident, either it be something as harmless as the beginning of the episode, or graphic detail of his crucifixion.
10) Alan and Glep are roommates in a shitty apartment.
11) Another difficult struggle is that Alan is very weary of non-cheese food products, or just new foods in general. Like if he were to say, eat a burrito, Alan would literally unwrap the entire thing just to check what's on it. If there's something he doesn't like, he'll either pick it off or refuse to eat it because "it was touching _____"
I'll add more if I can think of any, but yeah. Pim is next!