The affable actor had a recurring part as Bobby Newport, who was both the future heir to the sugary Sweetums company, as well as Leslie's Pawnee City Council opponent who could care less if he wins the job.
The Key & Peele actor recurred as Joe, who went from being introduced as Donna's ex-boyfriend to her husband by the end of the series.
The Saturday Night Live alum had a memorable, hilarious part as Carl Lorthner, the literally loud-mouthed Parks Security employee.
The Will & Grace alum made a brief appearance on the show as Buddy Wood, a big-time reporter from Indianapolis who interviews Leslie as she runs for city council and insults Pawnee in the process.
Dax Shepard showed up in the show's final season as Hank, the boss at the TV studio that aired Andy's program "Johny Karate."
Jonathan Banks played Ben Wyatt's dad, Steve, on the show, a far cry from his terrifying role as a hit-man on Breaking Bad.
Before starring in Brooklyn Nine-Nine, Chelsea Peretti had a small role on-screen as Zelda, a woman at a city council meeting, but had a larger role behind-the-scenes of the show as one of its staff writers.
The Roots drummer Questlove made a fun appearance in the series as Levondrius, Donna's estranged brother.
The U.S. Senator, who is dating actress Rosario Dawson, makes a cameo on the sitcom.
The West Wing alum plays Councilman Larry Pillner, whose seat Leslie fills after she runs for city council.
The comedian played Chipp McCapp, a country musician whose music video "Beautiful Like My Mom (Support the Troops)" was hilarious, and kind of a bop.
We saw Jon Hamm's comedy chops when he showed up as Ed, a National Parks Service employee who Leslie calls "the most incompetent person" she's ever met.
The Leftover's Justin Theroux played Justin Anderson, one of Leslie's boyfriends before she found her happily-ever-after with Ben Wyatt.
The now-Democratic Presidential nominee was a favorite of Leslie Knope's back when he played himself in Barack Obama's administration.
Leslie Knope could barely even speak when she met up with one of the best First Ladies of all time, Michelle Obama.
The Good Place's Kristen Bell appeared on this NBC sitcom as well when she played Ingrid de Forest, a stuck-up councilwoman from Pawnee's rival city, Eagleton.