Released on their 1988 album Green but intended for 1989 single release (hence the title), the story of this song isn't really the song - which is a pretty standard pop song parody lyrically, and unimaginative in its simplicity musically. The video featured three topless women and a topless Michael Stipe dancing. This is the age restricted video you can't see below.
However, you can't show nipples on MTV. So, Michael Stipe put black bars on all the nipples, including his - because, as he said, "a nipple is a nipple."
It's rare that a B-side to a single is the same as the A-side, and yet, an acoustic version of "Pop Song 89" was the B-side. It is, in my opinion, a better version of the song - showing the beauty of the arrangement and the biting parody of the lyrics a little more pointedly.