Tim Tebow -- No on Abortion, Yes on Contortion

It's not every day that Tim Tebow agrees to hang out with a bunch of chicks who can put their legs behind their back ... but hey, Vegas is a special place.

The Denver Broncos QB went behind the scenes at Cirque du Soleil's "O" this week ... posing for pictures with some of the incredible flexible performers after taking in a show at the Bellagio.

As we previously reported, Tim was only in town for a few hours for a Nike photoshoot ... and stayed away from all of the usual Vegas temptations -- gambling, partying, buffets.