Son of Schmilsson was released while Nilsson Schmilsson was still on the charts. It hit #12, spent 31 weeks on the charts, and went gold.
At the end of the Son of Schmilsson album Richard Perry says "Goodbye, Harry" to which Harry replies, "See ya next album, Richard."
According to Nilsson expert, Curtis Armstrong, this was something of an inside joke. During the "I'd Rather Be Dead" sessions Harry and Richard brought in the Stepney and Pinner Choir #6, a group of senior citizens, to sing on the track. The day turned into something of a party for everyone. At one point, Harry and Richard were up in the booth listening to a playback with Klaus Voormann when they heard a weird sound on the recording. They played it back over and over trying to determine what it was. Finally, Voormann, who Harry claimed has ears like no one else on earth, said it sounded to him like a wooden leg creaking. This put Harry and Richard into a bit of a bind, as they were a little embarrassed about asking a roomful of pensioners if any of them had a wooden leg. But there seemed to be little choice as the clock was ticking on the session which had already gone on for hours. Richard, very apologetically, asked if there was anyone in the room with a wooden leg. "I 'ave!" said one. So they asked him to please try and keep still while the tape was rolling. At the end of the session, as the Choir were headed out for the bus and saying their goodbyes, the fellow with the wooden leg tipped his cap to Harry and Richard and said, "Well, see ya next album!"
Songs come differently each time, each album is unique. In Africa, the year before last, I wrote the Schmilsson album in a month and a half. I was never that prolific before and probably never will be again. There was no telephone going off. There were elephants outside. I took out a notebook and a pen and, wow. all of a sudden I started writing lyrics and melodies without being near a piano or guitar or anything.
-- Harry Nilsson 
-  Citation Needed.