Do you know what backmasking is?
No? I'll tell you. Backmasking is messages which can be found when a song is played in reverse. An example of this is Another One Bites the Dust, which reverses as It's Fun to Smoke Marijuana.
Another, longer, example is Stairway to Heaven.
"If there's a bustle in your hedgerow, don't be alarmed now,
It's just a spring-clean for the may queen..."
And the rest of that verse reverses as:
"Oh here's to my sweet Satan,
The one whose little path would make you sad whose power is Satan,
He'll give those with him 666,
There was a little tool shed where he made us suffer, sad Satan!"
What other examples can you find?