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(USATODAY.com) - She even participated in "Ew!,"a silly skit with Fallon and Ferrell playing bratty little girls being fed kale chips by health-conscious FLOTUS.

The ostensible reason for her appearance was to mark the fourth anniversary of herLet's Move!anti-obesity and healthy-eating campaign, which she described as making a measurable difference around the country.

But she also got in plugs for her new campaign to encourage kids to aim for college, and for the Obama administration's effort to get more young people to sign up for theAffordable Care Act, aka Obamacare.

But it may be that Mrs. O just likes going on late-night talk shows and yucking it up with funny guys, especially the puppy-like Fallon. The pair have appeared together twice before, including their memorable "Evolution of Mom Dancing" dance skit last year, now a YouTube hit (about 17.2 million views).

She's turned up on late-night shows more often than any of her predecessors, hitting all the majors, including Fallon predecessorJay LenoandDavid Letterman.

But she and Fallon do seem to get on: She praised him for helping with the Let's Move campaign, he called her appearance on the show "an incredible honor."

For her session on Fallon's couch, Obama, 50, looked chic in a silky black palazzo pants-and-sleeveless-top outfit accessorized with a wide black leather belt at the waist. Earlier, during the skit, she wore black slim pants with a bright orange-red sweater tunic.

And that was only two of her outfit changes on Thursday; she started the day off at theNew Museumin New York, dressed in a skirt with a striking watercolor pattern. And, as a reliable fundraiser for the Democrats, she also attended a fundraising event at the home of an important Obama fundraiser in New York.