Double-T (portrayed by David Patrick Kelly) is a homeless poet who is best friends with Rob and his real name is Thomas Norburt. He nicknamed his first name and changed the letters around in his last name and called himself Tommy Truborn.
Double-T's first appearance was in "Into the Comics". He was telling one of his poems at a recreational center when Rob met him. Double-T was Rob's mentor and gave a few pointers in terms of writing. He also helped Rob in figuring out how to reason with his father.
He then appeared in the following story arc "To the Light" where he was a major character in that particular case, when the corner he was working on was ramsacked. This was also the case where he ran into his daughter Lisa.
Then in second part of "Who's Who?" Rob mentioned that he and his dad were going to help him find a home.