Actress Tilda Swinton befuddled visitors at NYC's Museum of Modern Art with a surprise visit that involved her sleeping (or appearing to sleep) inside a glass box.

It's an art exhibit dubbed 'The Maybe' -- and we're guessing David Blaine is probably pretty pissed that he didn't think of it first.

'The Maybe' was first performed in 1995 at London's Serpentine Gallery and also at the Museo Barracco in Rome. Swinton's premiere appearance in the New York installation occurred on Saturday (March 23), and according to the Gothamist, her presence startled and delighted visitors who were eager to get a snap of the actress.

Take that, modern art. You may not make sense, but add Tilda Swinton to the mix and suddenly people get excited about you.

"Museum staff doesn't know she's coming until the day of, but she's here today," a MoMa source said on Saturday. "She'll be there the whole day. All that's in the box is cushions and a water jug."

The museum has confirmed that Swinton will show up at least a half-dozen more times between now and the end of the year, "each unannounced and in a different location in the Museum."

In an official statement, MoMa added:

“An integral part of The Maybe's incarnation at MoMA in 2013 is that there is no published schedule for its appearance, no artist's statement released, no museum statement beyond this brief context, no public profile or image issued. Those who find it chance upon it for themselves, live and in real -- shared -- time: now we see it, now we don't."

For her next trick, Swinton will count blades of grass in Central Park inside a giant inflatable bubble.