The actress was on the US show to promote new movie FLIGHT PLAN and Gibson thought it would be funny to carry his MAVERICK co-star out on stage.
Gibson, sporting a bushy beard, agreed to make a brief appearance on the late night show so he could sign a Harley Davidson motorbike host Leno is auctioning off to raise funds for the ongoing Hurricane Katrina relief effort.
Funnyman Leno took a moment to poke fun at the movie mogul, introducing him as GRIZZLY ADAMS and then joking, "You can't sign as MOSES, you have to sign as Mel Gibson."
Meanwhile, Foster was thrilled with her entrance, stating, "It was a little King Kong moment... I'm gonna hire him from now on wherever I go; I just get carried in."
And she admitted she loves Gibson's bearded image: "It's a good look, don't you think?"