The Emmy award-winning star - who penned episodes including Boy-Scoutz 'n the Hood (1993), Bart of Darkness (1994) and Homer's Phobia (1997) for the world's longest-running animated series - died on Friday at NYU Langone Hospital in Brooklyn, New York, following a stroke, his sister Gail Garabadian, told The Hollywood Reporter.
"We lost my incredible brother Danny yesterday. He was a special man, one of a kind. An incredible son, brother, uncle and friend. Our hearts are broken," she wrote on Facebook.
Tributes have since poured in for McGrath - who also co-wrote Treehouse of Horror IV's The Devil and Homer Simpson (1993) and Treehouse of Horror V's Time and Punishment (1994) with Greg Daniels.
Former The Simpsons writer and showrunner Bill Oakley, 59, hailed McGrath as a "great person".
He wrote on X: "R.I.P. today to Dan McGrath, great person and super-talented writer at The Simpsons, SNL, King of the Hill, and Mission Hill … He brought so much joy … You were a real one, Mr McGrath. You'll never be forgotten."
Fellow former The Simpsons writer and showrunner Josh Weinstein, 59, said McGrath was "one of the funniest - and kindest - writers and an unsung hero on all the shows he worked on".
"RIP to one of the sweetest, funniest souls we ever had the pleasure to work with and know," he said on X.
McGrath began his career as a writer on the sketch comedy show Saturday Night Live, and he frequently worked with comedian-and-actors Adam Sandler, 59, and the late Chris Farley.
He then moved to work on The Simpsons, where he bagged writing credits for 50 episodes, released from 1992 to 1994, as well as producing 24 episodes released from 1996 to 1998.
He won the Outstanding Animated Program Emmy for his work on the 1997 episode, Homer's Phobia.
The episode sees a gay antiques dealer called John (filmmaker John Waters) be befriended by Marge (Julie Kavner), and Marge's husband Homer (Dan Castellaneta) becomes friends with John.
McGrath was also honoured by GLAAD for the episode's anti-homophobia message.
After he got fired twice from The Simpsons, he worked on Mission Hill, Gravity Falls, and spent eight years contributing to episodes for King of the Hill.
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