One of the most beautiful friendships is the one between Bowie and Iggy. Like I just said, Bowie helped Iggy in the 70s by co-writing songs with him and producing his albums. In the early 80s, when Bowie was at his peak as a chart hitter, he covered Iggy's songs in his albums, ensuring royalties for his friend. eg. China Girl, Tonight, Neighbourhood Threat. Both collaborated on Iggy's Blah Blah Blah (1986). That album was a turning point in Iggy's career.
Go watch Bowie and Tina Turner's take of Tonight on youtube.