I made this money butterfly for my best friend birthday. I think it's a lovely idea to give money like this instead of a simple envelop.
Take two bills. One bill, original size and one bill made smaller by folding the sides. The rest of the instructions are for both bills.
Fold it double lenghts wise.
Fold bottom towards the center line.
Fold top towards center line.
Open the bill.
Fold all four corners towards the center line.
Turn the bill.
fold small line in.
Turn the bill and fold a small line in.
Do this until the paper is like picture above.
Take some iron wire and pliers. Push both bills together and twist the iron wire around it.
Cut the iron wire and bend in to antenna shape.
This is how it should look like. I placed it in a special envelop and closed it with some ribbon and a tag.