Jane Krakowski put it ALL out there -- boobs and butt included -- for a lounge singer styled performance totally reminiscent of her "30 Rock" days.
Jane was the showstopper of the night at a gala for the Roundabout Theatre in NYC on Monday ... and never missed a beat when her full ass crack and nipples were exposed.
Check out the pics -- the "Unbreakable Kimmy Schmidt" star's still got plenty of Jenna Maroney left in her.
See also

Jennifer Lopez -- My Ass Needs Air!!!

Britney Spears -- Help, I'm About to Flash Everyone! (VIDEO)
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