Tilda Swinton -- Take a Look Inside, She's Asleep in a Box!

Someone call security, there's a homeless woman sleeping in the Museum of Modern Art! Oh wait, that's just actress Tilda Swinton, who is there as part of a performance art piece.

The display is called, "The Maybe" ... as in maybe Tilda will be there, maybe she won't -- there's no advance warning for when she shows up for a snooze.

The Oscar-winning actress pulled the same stunt art in 1995.

Fun fact: You can catch a similar display of high art ... in a random alley of any major city.