If you dial 1-800-STAMP24, you can purchase postal and hunting stamps. Among these are "duck stamps," the adhesive seals the Federal government requires waterfowl hunters to carry in order to hunt the birds legally. In the past, the government has printed this 800 number directly on the stamps, in order to allow hunters to order more.
I just dialed the number myself. It's a pretty boring standard automated message. Evidently someone at the "duck stamp" program agrees. This year's stamps, instead of some dull robocall, come printed with the number of a phone sex service.