"Here in my hand is Fred the Trained Flea. Fred will perform for you some amazing feats. Watch closely."
"Fred, do jumping jacks! Very good! Cheer, everyone!"
"Fred, do a somersault!"
"Fred, do a high jump!" Watch him go way up, then back down.
"Now Fred will do a long jump. I need a volunteer to catch Fred." Pick a scoutmaster or someone in authority.
"Fred, do a long jump!" Watch Fred jump to the volunteer "Oh! He seems to have jumped into your hair!"
Walk over to the volunteer, start picking through their hair. "Here we are .. no, that's not Fred." toss the flea over your shoulder "Ah! No, that's not Fred." "That's not Fred." "Fred, are you in there?" "That's not Fred either." "Boy, there's a lot of fleas in here." "Fred? Fred?" …