This is a 'trick to figure out' type activity, along the lines of Chinese Numbers
Hold your left hand up with all fingers spread out.
Touch the index finger of your right hand to the tip of your left pinky, ring, middle, index fingers, then slide it down the slope to your thumb and touch the tip of your thumb. Then slide up the slope from thumb to index and touch the tip of each finger in the opposite direction.
While doing this, you chant "Jimmy, Jimmy, Jimmy, Jimmy, Woop, Jimmy, Woop, Jimmy, Jimmy, Jimmy, Jimmy." Jimmy each time you touch a fingertip and Woop when sliding up or down the slope.
Then, you ask the others in the group to repeat what you did. Obviously, pointing to your fingertips and saying the right words is what is expected.
The trick is that you do something right before and/or after the fingertips that is part of the steps to repeat. For example, clear your throat or cross your arms or say "OK, here we go" or any other thing. It's best that you use an action that you can make more and more obvious the longer it takes people to figure out so you can help them "get it".