Sony made us. I'm not saying it was the wrong decision ultimately, but the honest answer to the question is that Pierce was literally the only role for which nobody else was considered after the actor we cast put his hat in the ring. Even McHale had to "test" against two other great guys. The short list of people I wanted to see about playing Pierce: Fred Willard, John Cleese, Patrick Stewart. That's a juicy role, man, there's a LOT of brilliant old dudes out there, but in the end, Sony felt (accurately) that Chase was a household name. And I remember Krasnoff saying to me, "listen, you make the decision on your pilot that gets you a series order. You take these things one step at a time." And there was wisdom there. Vile wisdom, but it's a vile industry. And I think the writers and Chevy ended up creating an unforgettable character.
On what really happened between he and Chevy that inspired those angry voicemails:
He refused to do the "tag" for the Digital Estate Planning episode (the 8 bit video game episode). In the scripted tag, Abed comes to Pierce with the thumb drive he took, and says "Pierce, I've been able to adjust some of the code for your Dad's video game and I've made a version I think you might like better." He puts the thumb drive into a laptop in front of Pierce. We cut to the laptop screen, where we see Pierce's avatar on a front lawn with the giant floating head of Cornelius. Every time Pierce presses the space bar, his avatar throws a baseball to his father's head, which gives him a thousand points and a "great job, son!" Pierce presses the space bar a few times, pauses, then leans over and embraces Abed and we fade to black. When Adam Countee pitched that tag, tears instantly rolled down my cheeks, and in point of fact, my eyes are getting watery describing it to you. It was the most important part of the episode and possibly one of the most important moments of the season. I was very upset to hear that it wasn't shot because someone didn't feel like shooting it, especially since it was literally the last day of shooting, which meant we'd never be able to pick it up. I regret nothing about how upset I got. My job was to care about my show……I heard from the people on set was that he didn't think it was funny. After he realized how upset I was about it, he said things in voicemails like "there was no script" (untrue) and "I have a weird relationship with the name Cornelius" (dumb, he had no dialogue in the tag). The real answer, I believe, is that he wanted to go home because he was tired. He probably didn't realize he was permanently damaging the episode by doing so because he often walked off set and then we would just pick up his shots later in the week. But this was the final shot of the season. The sets came down after he walked away. So this was the one time in three years that his personality caused unfixable damage to something I really held valuable.
I don't know if this is good news or bad news but I tried not to think too far ahead too specifically. I knew that we had to generally get the audience used to the idea that Greendale, the campus itself, was NOT NECESSARILY INSTRUMENTAL to the long term viability of the show. That's why we did episodes like Remedial Chaos and Annie's Move and Abed as Batman, that's why we moved Annie into Abed and Troy's apartment and put Shirley and Pierce in business together...because the simple fact, to me, was that as much as we loved Greendale, we had to "complete" the story of Jeff Winger getting his four year degree. You can actually see one my "fourth season" ideas getting bumped up into the end of season three, because Jeff Winger has to decide, at the end of season three, that even though he's endured Greendale for the express purpose of getting his old life back, in the end, he has to choose Greendale over his old life, because Greendale has made him a better person. The fact that it happened at the end of season three is because at the time of writing the script, I had a sneaking suspicion that either the show or its creator would not be back for season four.