It's so simple!
Show your friend this envelope and ask him if he's ever seen a real rattlesnake egg.
Give it a big buildup!
Mention that the eggs are supposed to be kept in a cool place, but you've had them in your pocket, which may have made them get warm- but you "hope not"!
The more you build up the story, the more cautious he will be about opening the envelope.
Make it suspenseful for the best effect!
When he finally peeks inside the envelope- BRRRRRTTTTTT!
he envelope vibrates with a loud rattling sound!
He's sure to be startled!
The mechanics are simple to operate.
Just twist the rubberband with the washer on it a few times, and place it, wound up, inside the envelope.
The rubberband will stay wound up until your friend peeks inside.
That gives the washer enough room to spin around as it unwinds, making that noise and vibrating against the side of the envelope.
A terrific practical joke, this one has been around for years.
The problem was, the only versions available were cheaply made and didn't have that loud, snappy sound that makes this novelty so funny.
WE'VE FOUND A SUPPLIER OF THE QUALITY VERSION, so we're carrying this one again!
WARNING: CHOKING HAZARD. Do not put the gimmick in your mouth. Not suitable for children under 5 years of age.