I found out the other day that I was once in my youth, around the late Paleolithic era, at the same concert as David Bowie.
In October 1991, Bowie and his then-band Tin Machine were touring their second album, imaginatively called Tin Machine II. On October 20, they had a night off between the Copenhagen and Stockholm shows, and went out to first see Bowie's old friends Kraftwerk at Solnahallen on the The Mix tour, and later Graham Parker and Mick Ronson at Berns. As it happened, I also saw Kraftwerk that night. I was 17, and it was only my second major concert (after Roxette at the local arena in my old home town a month earlier), and the also first time I visited Stockholm on my own.
The story doesn't tell if he got to hang out with Ralf and Florian, or if anyone in the crowd recognised him: "Fuck me, you look just like David Bowie!" "Yeah, I hear that a lot..."
Source: Timo Kangas' review of Tin Machine's Stockholm show, Göteborgs-Posten, 23 October 1991, p. 30. I only found the review three days ago, a third of a century after the fact; not that it would have mattered, of course, as I'd hardly heard Bowie at the time and was just starting my musical self education.