Imagine the following scene:
Husband and wife return home. Wife takes a large envelope from the mail box, and proceeds to unlock the door. Once inside, she looks at the envelope. Husband, entering behind her, spots the label on the envelope, sees that it says "Sheldon Comics" and snatches it from wife, exclaiming "Don't look at my mail!". He throws it face-down on the table to hide the label. Wife points out that there is a label on what appears to be the other side of the envelope that gives her name. Husband and wife discover that a) their local mail man bundles envelopes to the same address with a rubber band, b) they both made an order from the Sheldon store, and c), there will most probably be a duplicate gift this Christmas.