Here's an interesting one. It's the snippet of Just Like That from the ABBA Undeleted medley, with the OOPS (Out Of Phase Stereo) audio effect applied.
If you've never heard about the OOPS effect before, you can find out more about it here.
Back to the song, and it's quite nice to be able to hear a bit more of the backing track, without that overpowering saxophone. You can also quantify the sheer amount of echo that has been added to the girls' vocals in the chorus during mixing. If you listen carefully, you can also just about make out the backing vocals.