Chevy Chase has a long history of being a miserable a-hole to everyone around him. It's safe to say he's pissed off nearly every person he's ever worked with. Things seemed to be going fine on Community until the end of the third season when he got himself into a feud with show-runner Dan Harmon.
Now, Harmon is gone, but Chevy is still a dick and still having problems with the scripts and the direction of his character. On the show, Chevy plays the old fart, villainous, and bigoted Pierce Hawthorne.
According to TMZ, he got into a heated discussion on set about his character and yelled out something along the lines of "What's next? Am I gonna say the word ni**er?"
Needless to say, he wasn't directing it at anyone or being particularly racist, but it's still kinda a dick move.
Chevy has since apologized.