ET crashed the actress' rehearsal with pro partner Pasha Pashkov in Los Angeles on Thursday, where she handpicked which characters from the comedy series would perform best (and worst!) if they were on the dance competition show.
Giving herself some time to think, Flannery -- who played the hilarious Meredith Palmer on The Office -- narrowed it down to two characters: Phyllis Vance (portrayed by Phyllis Smith) and Dwight Howard (Rainn Wilson).
So, who would get the mirrorball trophy and who would be the first one sent home?
"I think Phyllis would kill it because she's a dancer," Flannery told ET's Keltie Knight. "You can actually tell on the show a little bit that she knows how to move."
And then, well, there's Dwight. "He can move, but I don't know if he can dance," she said. "He knows everything, so he couldn't learn, right? Unteachable, but he would raise and lower his cholesterol at will, for no reason."
All jokes aside, Flannery is, indeed, already killing it on DWTS! During Monday night's show, she danced the Foxtrot to "Fly Me to the Moon" with Pashkov, and the two received a score of 21/30, the second-highest of the night.
"There are no words. I was speechless, and I'm never speechless," she exclaimed. "I talk too much. I should shut up and dance."
"This is a complete shock to me," she added. "This is all this guy. Seriously, this new pro, Pasha, is the best. The best! He's my secret weapon."
Rehearsals for next Monday's Movie Night are already underway, and Flannery admitted to ET that she's "already had 14 panic attacks."
"This is the thing, you have less and less time as the show goes on," she explained. "I was like, 'We have to take a day off?' It kind of freaked me out. But I'm learning to trust because Pasha knows what he's doing ... my life is in [his] hands. No pressure."
Pashkov chimed in, noting that her body is getting more tired as the days go by, something Flannery has been documenting in her DWTS diary posts on social media. "We get less and less time to learn new choreography," he said. "Each dance is very different, so even though Kate mastered her Foxtrot, this week it's a completely new dance and technique."
"And now that Mary Wilson is gone and Christie Brinkley, I am the old broad on the show," Flannery, 55, joked. "But there's no mercy. I'm doing it loud and proud, baby!"
Flannery and Pashkov couldn't reveal which movie they'll be channeling next Monday, though by the clues ABC dropped via Instagram, it appears the duo may be performing a piece inspired by 9 to 5.
"I'm having a great movie in my [own] life right now, I really am," Flannery shared. "Seriously, no matter what happens, I feel like a winner. I really do."
To see how #TeamThat'sWhatKateSaid's week three rehearsals paid off, tune into Dancing With the Stars Monday at 8 p.m. ET/PT on ABC. In the meantime, hear more from their competitors in the video below.