In the Stephen King novel 11/22/63, the protagonist, Jake Epping, goes under the name George Amberson when he goes back in time to prevent the JFK assassination.
In the Stephanie Plum series by Janet Evanovich, Stephanie frequently pretends to be a hooker or a bimbo in order to throw off the skips she's supposed to be catching (she's a bounty hunter).
In the classic novel Ramona by Helen Hunt Jackson, Ramona changes her name to Majella when she runs off with her lover.
In Les Miserables, by Victor Hugo, Jean Valjean goes by the names Monsieur Madeleine, Ultime Fauchelevent, and Urbain Fabre in order to hide his past.
In Shakespeare's As You Like It, Rosalind flees persecution at court and disguises herself as a young man named Ganymede.
