Pregnant Man Doing LMFAO for Halloween -- I'M SEXY AND I KNOW IT

Pregnant Man Thomas Beatie has passion in his pants and he ain't afraid to show it ... dressing up as Redfoo from LMFAO for Halloween this year -- and his costume's incredible.

Thomas tells TMZ, "I've pretty much been obsessed over the last month trying to get my Redfoo costume together" -- a massive waste of time because the costume's literally just a t-shirt, animal print stretch pants, and his GF's old Richard Simmons wig.

Thomas adds, "I've been Googling the moves, so I plan on being in true character come Halloween."

FYI -- if you're wondering what the black bars are covering ... let's just say Bush wasn't just the 41st President of the United States.

Thomas says he tried reaching out to Redfoo on Twitter to see if the LMFAO rapper would want to do a costume trade -- suggesting Redfoo could dress as "The Pregnant Man" by stuffing a pillow under his shirt.