Il a fait des études à Yale, où il a découvert son homosexualité en première année.
Il scénarise actuellement Young Avengers pour Marvel Comics, et a été scénariste et producteur de La Vie à cinq (Party of Five), Sex and the City, Gilmore Girls, ainsi que coproducteur exécutif de la série de la Fox Newport Beach (The O.C.).
Heinberg partage le même atelier d'écriture que ses camarades scénaristes Jeph Loeb et Geoff Johns.
- You're right. I have to tell them.
- They'll understand. And if they don't, you can always zap them with your magic powers and make them undestand. Then you can zap my mom.
- and that Lieutenant America was--acording to Farrell here--extremely bossy.
- He told me to move, like, ten times.
- Where were you?
- In his face, asking him questions.
- While he was trying to put out the fire?
- What's your point?
- So...Jonah wanted to be Bucky when he was a kid. That explains a lot.
- Not really. What kid doesn't want to be a super hero? To have the perfect body? Be able to fly?