Harmon confirmed over the weekend that he had been fired by Sony Pictures Television and will be replaced by Happy Endings writers David Guarascio and Moses Port.
McHale – who said last week that he was "literally praying" for Harmon's return – took to Twitter over the weekend to thank his former boss.
"[Dan Harmon,] you are a true genius. You gave me the role of a lifetime & three of the best years of my life. Buying #Prototype2 today," McHale wrote.
His co-star Brie also weighed in on Harmon's axing by tweeting that she is honoured to be a part of the Community cast.
Brie tweeted: "I'm in creative debt to @danharmon who let us ride the coattails of his integrity, pushing boundaries & making f'ing awesome tv. Thanks Dan."
Community's Gillian Jacobs, Yvette Nicole Brown and Jim Rash also thanked Harmon on Twitter.
Harmon's firing comes on the heels of a series of public feuds with Community star Chevy Chase, but it is unknown if their clashes played a role in Sony's decision.
Community was renewed for a fourth season by NBC last week.