There is no end to good old baking soda/vinegar fun. Here's a Halloween (or not) spin on it!
You'll need baking soda, vinegar, a latex or vinyl glove, and a cup.
Pour some vinegar into the cup
add some baking soda into the fingers of the glove.
Place the glove onto the cup without getting of the baking soda into it just yet.
When you're ready, pull up the fingers so the baking soda dumps into the cup
Nice to meet you.
Be prepared to repeat. Have fun!