Rubber Check

A man walks into a drugstore and asks the pharmacist for a pack of condoms. Paying for them, he bursts into laughter and walks out of the store. The next day he comes in again, again buys condoms, and again walks out laughing. Thinking this is somewhat strange, the pharmacist asks his assistant to follow the man if he comes back. Sure enough, the man comes in the next day and walks out laughing. This time the assistant goes after him, returning 20 minutes later.

"So did you follow him?" asks the pharmacist.

"Yup."

"Where did he go?"

"Your house."