Imagine you're riding the subway, when suddenly the first Darth Vader/Princess Leia scene from Star Wars breaks out around you. Full costume, complete dialog, the works. That's exactly what happened to some very lucky straphangers this past summer.

MP3 Experiment 6

Like this year's, but replace "Bryant Park" with "Roosevelt Island" and "large-scale zombie dance" with "large-scale do-si-doing." Keep the overwhelming sense of joy.

Who You Gonna Call?

You could wait around for Dan Aykroyd to finish up that Ghostbusters 3 script, but the instant gratification crowd should appreciate this return to the NY Public Library Improv Everywhere staged earlier this year.

The Camera Flash Experiment

Not so much a prank as a large-scale tribute to the Brooklyn Bridge; a week before the landmark's 125th birthday, 700 Improv Everywhere "agents" used their camera flashes to create a wave of light linking Manhattan and Brooklyn.

Best Buy

Best Buy sure is fond of their blue shirts. Less so, though, when 80 people dressed as Best Buy employees flooded a Manhattan store back in 2006.

Megastore

At the since-deceased Virgin Megastore in Union Square, the Improv Everywhere team took over 35 adjacent listening stations and stood at attention. That would've been fun enough on its own! But then? Then with the glorious choreographed dancing.

Cellphone Symphony

Another retail invasion, this time at the Strand bookstore. 60 cubbies for bags at the front of the store, each containing a cellphone, all ringing at the same time. Then again, but broken down by brand. The only downside? The people outside not being able to hear the fruits of their dialings.

The Moebius

An earlier mission, and maybe my all-time favorite: in a Manhattan Starbucks, seven people repeat the same five minute sequence of events—for an hour. It's a time and mind-twisting social experiment that left customers confused, and makes me want to slow clap every time I watch it.

For detailed background information on these other equally great (but less geeky missions), or to sign up to participate in future ones, head over to Improv Everywhere.