Trekkie Monster is a character from Avenue Q. He lives on the second floor of one of the buildings. In early drafts of the musical, Trekkie Monster was an obsessive Star Trek fan, hence his name. He even wore a Star Trek-like tunic and sported pointy Spock ears, but concerns over copyright issues with Paramount forced a change to that concept. He kept his original name, however. Trekkie Monster is a parody to the Sesame Street character Cookie Monster. His speech pattern also resembles that of Cookie Monster. He was originally performed on Broadway by Rick Lyon, who created all of Avenue Q's puppets.
He is obsessed with collecting and looking at internet porn, just as Cookie Monster is obsessed with cookies. He also has made millions (perhaps billions or trillions) of dollars investing in pornography on the stock market. Trekkie also sings most of the song "The Internet is for Porn," which has become a popular internet meme.
For two days mini hand-puppet versions of Trekkie Monster sold at the opening of the London Avenue Q. These puppets are now highly valued among collectors.