A Balloon Adventure
As kids, we all enjoyed playing with balloons, so any idea involving balloons will awaken a playful and childlike smile deep in our memories. This effect doesn't go unnoticed by a good romantic, so we'll use it to give a delightful surprise.
The most basic and simple idea is to decorate a room with balloons for any occasion, whether it's a special date or just an ordinary day when you feel like surprising someone. Be imaginative; there are many types of balloons, with different textures, shapes, colors, and designs.
A step beyond is to literally flood the place where you plan to surprise your 'victim.' In this case, you'll need a large number of balloons, as, for example, a hundred barely covers the floor of a room about 9 square meters. This means you'll need to arm yourself with patience and air to fill the necessary balloons to flood a place. If you can have a friend lend a hand, even better. The final result should resemble a ball pit like those for small children, but filled with balloons in this case.
Our balloon pit allows for various enhancements that can make the surprise even more special. For example, you can fill some balloons with notes, so after being popped, the surprised person can be doubly surprised by reading a compliment, a clue to where you've hidden a gift, or a spicy action to perform.
In the same vein, you can create a simple game: you have to do what the note in the balloon says. Fill many balloons with notes, and you'll have a fun (and who knows, maybe spicy) way to enjoy several hours with your partner.