For the show's address and more information on how you can send them fan mail, check out this page: /heathers-the-musical.html
This is an AMAZING response and I'm super impressed by how quickly they sent it! Thank you so much Heathers!
[Specific Cast Member or Stage Manager]
New World Stages
c/o Heathers: The Musical
340 West 50th Street
New York, NY 10019