The song "Human Nature" replaced the song "Carousel" on the Thriller album.
"Human Nature" would not have been included on Thriller if it weren't for forgetfulness. While producing Thriller in 1982, both Jackson and Quincy Jones had planned to include the song "Carousel" (now an outtake) on the album, as there was room for just one more "mood-like" song, as Jones puts it. However, Jones believed that "Carousel" had to be taken out and replaced. During this time, Toto sent Jones two demo tapes that they thought would be suitable for Michael.
The first two songs on the demo tape did not impress Jones. After the first two samples, Jones forgot to turn the tape off. It was at this moment, as Jones describes it on the special edition of Thriller, that "...and all of a sudden there was all this silence, and then it went "why? why?...da da da da da da da da...why? why?". While talking about it, Jones mentions that he gets "goosebumps from just talking about it".
It was this demo, written by Porcaro, that Jones decided to take Carousel out of the album, and was then replaced by "Human Nature", partly due to its "wonderful flavour". Jones then contacted Bettis to write a lyric to the song.