A man walks into a pharmacy, buys a condom, then walks out of the store laughing hysterically. The pharmacist thinks this is weird, but, hey, there's no law preventing weird people from buying condoms. Maybe it's a good thing.

The next day, the man comes back to the store, purchases another condom, and once again he leaves the store laughing wildly. This piques the interest of the pharmacist. What's so funny about buying a rubber, anyway? So he tells his clerk "If this guy ever comes back, I want you to follow him to see where he goes."

Sure enough, the next day the laugher is back. He buys the condom, starts cracking up, then leaves. The pharmacist tells his clerk to go follow the guy. About an hour later, the clerk comes back to the store.

"Did you follow him? Where did he go?" asks the pharmacist.
The clerk replies "Your house."