Go on a search for as many good climbing trees as possible, climb as high as you both can in all of them, compile photo evidence.

Go to a major chain bookstore and leave notes to future readers in copies of your favorite books.

Have her dressed up as a ghost and you dress up as PacMan. Walk around downtown holding hands, and wherever anyone sees you two, pretend to be embarrassed and run off screaming, “wocka, wocka, wocka.”

Create photo evidence suggesting that you went on a fantasy adventure.

Dress up as superheroes and stop  at least one petty crime, i.e. jaywalking, littering or help someone in need.

Build forts out of furniture and blankets, then wage war with paper airplanes.

Try to visit as many people as you can in one night, and turn as many things upside down as you can without them noticing.

Go to the airport, get the cheapest, soonest departing flight to anywhere when you show up, and stay there for the weekend.

Write a piece of fiction together in an outdoor cafe and ask strangers for help when you get stuck.

Do the lamest tourist thing in your area that you have both secretly wanted to do forever.

In the middle of the night, drive to the beach so you arrive right when the sun is rising. Have a breakfast picnic, then fall asleep together. Bring a sun umbrella.

Drive somewhere unknown and have dinner in a city you’ve never been to while using fake names. Pretend you are either secret superheroes or spies.

Go to a minor league baseball game. Tell each other stories about how bad you are at athletics. Randomly cheer for both teams. Eat lots of Cracker Jacks. Complain that the pitcher failed to make the “Field Goal.”

Go around your city with sidewalk chalk and draw hearts or random, made up math equations in odd places.

Walk around the city and perform silly silent plays in front of security cameras.

With a camera and a pair of shoes, make a photoblog of a day in the life of the Invisible Man.

Go to a restaurant and convince the chef to create something completely new for you.

Rent a movie neither of you have seen before, mute the sound and improvise the dialog for the whole thing.