My Wonder-Red headcanons part 3:
His favorite season is spring. He likes the symbolism of starting anew, and enjoys the blooming flowers and trees turning green. He could do without the pollen though.
Of the main 7 Wonderful-Ones, he gets along best with Wonder-White. Pretty sure this is actual canon, but it's not explicitly mentioned. Still shocked I've never seen ship art of them.
He has a very basic Halloween costume of a honey bee that he just reuses every year. His students think its cute, but also lazy. He hasn't gotten around to updating the costume.
Meanwhile he has a bazillion Christmas sweaters and wears a different one every day of December. His students think it's funny, but also accuse him of having a weird obsession with sweaters, but he just loves Christmas.
He occasionally watches children's shows and plays E-rated video games to better understand the things his students are into. He finds that he's able to connect with them on a deeper level when they see he understands what they're talking about and can engage with them on their level in their interests. Sometimes a student will bring up a specific episode and talk about whatever part was funny, and Will will reply with some evaluation of the messages and morals in the media that he thinks his students should take in and critically analyze. This brings him and his students much closer, making them more comfortable with sharing their emotions with him about things that are bothering them either at school or in their home lives. He's like a third parent to them.
His favorite fairy tale is Pinocchio.
As a child, immediately following the death of his father, he'd cry himself to sleep every night and wake up thrashing and screaming, having agonizing nightmares that would exaggerate his trauma. It was such a problem, Nelson moved the furniture away from Will's bed and put the mattress on the floor so Will wouldn't fall off and hurt himself. Nelson couldn't realistically just watch Will sleep to make sure he wasn't going to hurt himself, so he gave Will a stuffed animal of a lion hoping it would comfort him. Child Will at first didn't like it, but one day chose to hold it while he slept, and the fluffy mane tickling his nose reminded him of his father's hair, and it invoked happier memories that comforted him. He had better sleep from that point forward. As an adult, he still owns the stuffed animal, but doesn't sleep with it anymore. His favorite animal continues to be lions for their symbolism in strength and leadership.
He is immensely well organized. He has kept nearly everything he has ever owned that isn't literal trash, and has everything neatly arranged in its own place. The only things he didn't keep were things from his early childhood that elicit painful memories. He still has some of those items, though.
Wonder-Future's file, that is to say child Will's, states that his hobby was weapons. Following Earth Defense War II, Will learned the true weight of war and distanced himself from his enjoyment of weapons and army stuff. He came back to it in his early adolescence with a deep respect for them as opposed to a childish admiration of them.
The only person he's ever spoken to about his trauma is Commander Nelson... and probably a therapist.