Whiskey no worms
A man drinks a shot of whiskey every night before bed.
After years of this the wife wants him to quit, so she gets 2 shot glasses, filling 1 with water the other with whiskey.
She gets him to the table with the glasses and has his bait box there too.
She says "I want you to see this." She puts a worm in the water it swims around. She puts a worm in the whiskey and the worm dies.
She says "so what do you have to say about this experiment?"
He says "IF I DRINK WHISKEY I WON'T GET WORMS!"