Grandpa and Grandma were spending a few weeks to visit with their son and his family. One night, Grandpa found a bottle of Viagra in his son's medicine cabinet. He asked him about taking one of the pills.
"Dad," his son replied, "I really don't think you should take one. They're very strong and besides that, they're very expensive."
"How much?" asked Grandpa.
"$10 a pill," was the answer.
"That ain't bad," responded Grandpa. "I'd like to try one. All I have are $50 bills, so I'll go break one and leave the money under your pillow."
The next morning the son found $110 under his pillow. So as soon as he could, he spoke to Grandpa privately. "Dad, you gave me $110 but I told you the pill only cost $10."
"I know that, son," Grandpa replied. "The extra hundred is from Grandma."