Try juxtaposing your hero and your antagonist's bios. Have them write up bios for each other in response. Have your secondary characters write bios for themselves and the main characters.
A handy tool is Characters Counter that keeps a running count as you type. (If that disappears, Google "160 character counter". Yes, apparently bios get 160 characters. Tweets are limited to 140. But wouldn't that mean a long bio would get truncated if retweeted? Hmm.)
Of course people are collecting best Twitter bios! 20 of the World's Most Clever Twitter Bios is a good start with links to several other collections.
Here's a sampling:
- I was named after a mythological being ... how would you feel?
- A man of mystery and power, whose power is exceeded only by his mystery.
- Marc is a man with a dream. A very simple dream, mostly involving nachos and beer, but a dream nonetheless.
- Currently starring in my own reality show titled, A Modern Cinderella; One Girl’s Search for Love and Shoes.
- I’m Kail, I was given a girl’s name when I was a baby because my parents are idiots.
- Former military guy & cop. Leprechauns freak me out.
- I have been called a PollyAnna, sugar-coated idealist. I like to think of myself as more optimistic than that
- Darth Vader: Community Manager for Sith Lord but tweets are my own. Asthmatic. Dad to two rambunctious Jedis. Love scrapbooking, Beyonce, and galactic domination.
- Hillary Clinton: Wife, mom, lawyer, women & kids advocate, FLOAR, FLOTUS, US Senator, SecState, author, dog owner, hair icon, pantsuit aficionado, glass ceiling cracker, TBD ...
- Tome Hanks: I’m that actor in some of the movies you liked and some you didn’t. Sometimes I’m in pretty good shape, other times I’m not. Hey, you gotta live, you know?
- Weird Al: You know... the Eat It guy.
- Anna Kendrick: Pale, awkward and very very small. Form an orderly queue, gents. Location: probably by the food.
- Lucy Hale: I drink too much coffee. And laugh too loud.