My daughter had a mermaid party for her 4th birthday. One of the activities was popping bubbles with your butt! They had a fantastic time and thought - hey lets do this again when it's snowy and we can't go out!
You don't have to be dressed like a mermaid to do this activity.
Some other variations I would do with this particular game is play music and when they heard the chorus try and pop it.
Play the ABC's on repeat and they have to try and pop it on their letter.
The possibilities are endless AND the giggles are contagious.