You choose your username when you sign up.
Labrinth's Twitter username is @labrinthda1st
Jonothan Ross's username on Twitter is Wossy.
Cory Monteith's Twitter username was @CoryMonteith
Dani Harmer's Twitter username is @MissDaniJHarmer.
Actress Alyssa Milano's username on Twitter is: @Alyssa_Milano.
There is no minimum number of characters that a Twitter username has to have. You can have a username with only one character, if you would like. There is a maximum number of characters that a username can have, though. A username cannot be longer than 15 characters.
To do a retweet on Twitter by someone famous you can either use Twitter's in-built retweet function or type 'RT@username' where username is the famous person's username on Twitter and press 'tweet'.
Her username is @katiewaissel24
His Twitter is @drewseeley
His Twitter is @DavisCleveland8
Her Twitter username is @kekepalmer
Yes you can change your username by going to your settings and changing the username displayed in the username box. See the related link for an article on this in the Twitter Help Center.