Chevy is the main reason I wasn't able to get into Community until the second season -- the Halloween episode. I kind of wanted to check the show out in season 1, but the thought of watching Chevy do those tired pratfalls and 1970's faux "confusion" bits kept me surfing right on past the show.
I once saw Chevy on the Tonight Show years ago, back when Johnny was till the host. The prop comedian, Gallegher, came out and did his fruit destruction thing and then went and sat down in the guest chair. Chevy, who had slid down the couch, apparently began making comments to Gallegher as he approached and then touched Gallegher's face. It all appeared to be a "bit" until Gallegher loudly stated, "Chevy don't like it when someone else gets a laugh", relieving us of the notion that this was a "bit". Chevy cannot NOT be an a-hole.
(BTW, Johnny's reaction to all this was shocking. He simply sat back in his chair and watched. Finally, he said something like, "I'm glad I'm at the point in my career where I don't have to be involved in stuff like this". For longtime Tonight watchers, this was crazy.)
Good lord, I couldn't stand him on Community. His scenes always brought an episode's momentum to a grinding halt. His character never appeared to "fit" in with the rest of the cast. Chevy had no trouble playing up the a-hole parts of Pierce's personality, but he totally lacked the ability to give the character charm and likebility.
My most fervent hope before Harmon was let go, was that they would drop "Pierce", never even mention his name again, and bring in a new actor in the same age group -- one who could relate to cast and show's followers. "Pierce" neded an actor with much more subtlety than what Chevy could provide. Just think of what could have been done with a 'Bill Murray' as Pierce, or in the Pierce spot in the cast.