Sneak peek: John Oliver returns to 'Community'

Patrick Ryan | USA TODAY

NBC's Community is inching one step closer to its goal of "six seasons and a movie," as the quirky comedy returns for a fifth on Jan. 2 (8 p.m. ET), and welcomes a slew of new and unexpected guest stars.

While it's unclear how most of these visitors will be put to use — among them, Breaking Bad's Jonathan Banks, Castle's Nathan Fillion and Arrested Development creator Mitch Hurwitz — John Oliver is returning as the snarky, alcoholic Professor Ian Duncan for a six-episode arc beginning Jan. 9.

Oliver last appeared in Season 2 as a psychology professor at Greendale Community College known for assigning countless dioramas and coercing students to participate in grueling, out-there research studies. After taking over an Anthropology 101 class (in which he showed YouTube videos and took shots with students), he eventually ran off once the dean (Jim Rash) discovered it was a blow-off class and Duncan was fabricating exams.

"Professor Duncan has such a vibrant relationship with alcohol that it's entirely possible he simply blacked out two seasons ago, and doesn't realize that he's missed anything," says Oliver, who filled in for Jon Stewart on The Daily Show over the summer and has an HBO talk show in the works for next year. "The truth is that there's actually a fantastic explanation for his absence that makes simultaneously complete sense, as well as no sense whatsoever."

Duncan makes his first appearance in the third episode airing this season, as the Greendale gang tries to solve the mystery of an anonymous bandit dropping coins down people's pants. While details are sparse on Duncan's role in the proceedings, we do know that he develops a bit of a crush on psychology student Britta (Gillian Jacobs).

"Duncan is attracted to anything with a pulse, as well as four things without a pulse," Oliver jokes. "Perhaps the most shocking thing you're going to see is Duncan demonstrating a single moment of basic human decency. Hopefully it's been worth waiting five seasons for."

The cast is thrilled to have him back as well, says Joel McHale, whose character Jeff Winger was once a friend and foe of Duncan, though he reveals they are now equals.

"I don't even know how to describe it. It's like having a childhood friend all of a sudden move into your apartment building and you guys are 25 and can party every night," says McHale of Oliver's return. "He's a good person and you want to be around him, but on top of that, he's one of the most intelligent people around. And on top of that, he's the funniest guy in the room."

Community fans gave a lukewarm reception to last season amid behind-the-scenes drama. Cast member Chevy Chase abruptly left before shooting was complete, and creator Dan Harmon — fired after the third season — is making a comeback after replacement showrunners David Guarascio and Moses Port (Happy Endings) left.

Harmon is "basically calling it a re-pilot of the show, where he's re-establishing all the characters and grounding (them)," McHale says. While it's not a total reset of the series, it picks up one year after the Season 4 finale, in which Jeff finally graduated from Greendale.

So does being a lawyer ultimately work out for him, or will Jeff become a Greendale Human Being once again? Although McHale can't say, he promises it's "one of our best seasons" and the show is "as sharp as it's ever been."

Oliver agrees: Harmon "has taken this season to a whole new level," he says. "I really hope that people watch, it's going to be great."