The 'It's Always Sunny in Philadelphia' star will reunite with writers John and Dave Chernin on the comedy, which she will also co-exec produce.

Fox is staging an It's Always Sunny in Philadelphia reunion.

The network has tapped Sunny star Kaitlin Olson to topline (and co-executive produce) the family comedy pilot The Mick, The Hollywood Reporter has learned.

From Sunny duo John Chernin and Dave Chernin, the single-camera comedy revolves around a hard-living, foul-mouthed woman who moves to affluent Greenwich, Conn., to raise the spoiled kids of her wealthy sister, who has fled the country to avoid a federal indictment. She quickly learns what everyone else already knows: Other people's children are awful.

Olson will star as Mackenzie "Mickey" Murphy (aka The Mick), a hapless mess, a wry-humored, hard-drinking, cigarette-smoking, living-large kind of gal, always "between" jobs and always broke. A scrappy survivor who's run out of options, she decides to pay her rich sister a visit, hoping for a little handout. What she gets, instead, is a full-time babysitting gig when her sister and husband are forced to flee the country in a hurry.

Should The Mick go to series, Olson would juggle both shows — as both are produced under the same corporate umbrella. (FX renewed Sunny for a 12th season back in 2014.) Her credits also include a voice role in Finding Dory, Vacation, The Heat and FX animated comedy Cassius and Clay, the latter of which was scrapped before its debut. Olson is repped by UTA and Haven.

The Chernin brothers will pen the script for the comedy, which landed at Fox after the duo and producers 3 Arts took the project out directly to networks. 3 Arts' Nick Frenkel and Oly Obst will exec produce alongside the Chernins and Randall Einhorn, with the latter set to direct the pilot.

Keep up with all the latest pickups, castings and eventual series orders with THR's handy guide to pilot season.