Hirsch is the creator of the Disney animated series Gravity Falls (2012–2016), in which he also voiced the characters Grunkle Stan and Bill Cipher.

He co-authored the companion book Gravity Falls: Journal 3 (2016), a #1 New York Times bestseller, and later wrote The Book of Bill (2024).

• He was a co-executive producer of the Netflix animated series Inside Job (2021–2022).