Everyone should get tested for STDs if they're sexually active, but some people drag their feet about it. And that's why a little shock therapy is often required. So this idea could be something to encourage people to get tested, using a familiar holiday song in a disturbing new way to get attention:
A man's and a woman's voice sing together:
On the first day of Christmas, my true love gave to me, a yucky venereal disease!
(Or: On the first day of Christmas, my true love gave to me, an unwanted STD!)
Then we would hear that record scratch sound effect (for the needle getting pushed off a record), and the announcer could remind everyone to get tested, or they might be giving unpleasant surprise "gifts" to their true love; and they might not love them back for it.
