Bowie told Paul Gambaccini in 1993 his recollection of the writing of Fame. He and Carlos [Alomar] had been working on the riff but getting nowhere when John turned up. The way Bowie tells it, Lennon's arrival inspired them that they quickly threw the song together, though Lennon's actual contribution was quite small. When they were jamming to Carlos' riff, Lennon kept singing "Aim" in a high-pitched voice. Bowie changed this to "Fame", wrote the lyrics, and that was pretty much the song. Strictly speaking, I don't think Lennon did enough to warrant an actual writing co-credit, but Bowie said he and Carlos decided to give him one anyway out of respect and also because they probably wouldn't have been inspired to write the song without his presence.

There's also another angle to consider. In 1975, Bowie was still trying to make his name in America, and Lennon was a much bigger name than Bowie. Bowie may have calculated that it was worth giving Lennon a credit to be able to say "I wrote this song with John Lennon". If that was his calculation, it apparently worked, because the song gave Bowie his first US #1 single.

I began writing with Paul McCartney, for his album Flowers in the Dirt, in 1987. We went on to compose a dozen songs together. "Veronica" was one of the very first songs that we worked on. It is a wishful song about my grandmother's failing hold on memory and reality. As the subject was so personal, I didn't find it easy to edit the song. Paul put some shape into the music of a rambling bridge and tightened up a few of the lyrical lines in the verses.