Yamamoto Genryusai—He's not naturally bald. The first time he tried out his zanpakuto, it backfired and mowed off all the hair on the top of his head.
Soi Fon—She joined the assassination squads – after losing that final 80 pounds.
Ichimaru Gin—When he first joined the Gotei 13, he was short, really short, shorter than Hitsugaya-short. Once he stupidly pointed his sword down and absentmindedly said "ikarosu Shinso", effectively shooting himself upward into a very, very tall tree due to the momentum and his extremely small body mass. It took five hours until he was noticed and rescued by some passing shinigami. He spent the next few years growing taller to ensure that it would never happen again.
Unohana Reitsu—She likes to believe the best in people. It took twenty years and the confirmation of just about every member of the Sereitei to convince her that there was something seriously wrong with the 11th division.
Aizen Sosuke—He is deathly afraid of the dark. Keeps a nightlight hidden under his bed. Once when Hinamori was cleaning out his room, she found it and took it, thinking it belonged to someone else. He spent the next three weeks camping out in the other divisions (most notably the third, where some psycho *cough* the captain *cough* was always setting off explosives) until a replacement was finally found.
Kuchiki Byakuya—One day, he lost that thing he wears in his hair (can't remember the name). After hours of fruitless searching, he decided to use a substitute for the day: pieces of uncooked Italian noodles. The humiliating thing: no one noticed the difference.
Komamura Sanjin—One time he got really drunk and sobbed out the story of how his family of hunting hounds chased him out of the house for all of Soul Society to hear. No one could keep a straight face around him for weeks afterward.
Kyoraku Shunsui—he sleepdrinks, meaning he would get up in the middle of the night and drown himself in all the liquor he could get his hands on. The next night, he would dream of a killer hangover. Then he would wake up and proceed to make it all reality.
Kaname Tosen—The day he joined the captains, they secretly held a meeting and had a pool on how many times he would crash into a wall in the course of one month. Ukitake won, with the surprisingly accurate guess of 178,449 (he was off by ½- the time when the ninth captain only bumped into a wall with the left side of his body). He gave the winnings to charity, incurring contemptible and hateful glares from those who placed the highest bets.
Hitsugaya Toshiro—He has an advanced case of the Napoleon complex, feeling the need to be more aggressive to compensate for his height. Tried that in the first few weeks of his captaindom. Ended up being viciously attacked by his peeved peers who were actually his superiors. Resolved to show his competence in the aspect of paperwork. (And work on his fighting skills.
Kenpachi Zaraki—cried the first time he read Katekyo Hitman Reborn! because he identified with Hibari Kyoya so much (the guy's catchphrase is "I'll bite you to death". Any fool can see they were meant to be bestest buddies).
Kurotsuchi Mayuri—When he was a child, he wanted to run away and join the circus as a clown. Some would agree that he was fulfilled that dream.
Ukitake Jyuushiro—He is a kind man with a terminal disease hanging around a bunch of psychopaths and weirdoes. Self-explanatory.
