Grandpa and Grandma were visiting the kids overnight, when Grandpa found a bottle of Viagra in his son's medicine cabinet.

He asked the son about using one of the pills, and the son said "I don't think you should take one; they're very strong and very expensive."

"How much?" asked Grandpa.

"$10.00 a pill", answered the son.

"I don't care," said Grandpa, "I'd like to try one, and I'll leave the money under your pillow as soon as I break this $50.00 bill."

The next morning the son found $110.00 under his pillow. He said to Grandpa, "I told you each pill was $10.00, not $110.00."

"I know," said Grandpa. "The hundred is from Grandma."