As we all know, there have been times when Genesis members have worked together outside the band who weren't actually even in the band at the same time -- Ant working with Phil and later with Steve, Steve working with Ray.
Does anyone know of anything like this from other bands?
The only case I know of is when a founding member of the Doobie Brothers, who left after their 1971 debut album, formed sort of a Doobies "tribute band" in the late 1990s with two other, almost bizarrely random former members. These two had been in the band quite a bit later, being members only for its 9th album from 1980 (plus a subsequent live album). (Seriously, imagine Peter Banks forming an alternate "Yes" with The Buggles and you'll have some idea how weird this was.)
Unfortunately this turned out badly because the actual, current Doobie Brothers ended up filing an injunction to keep the "tribute band" from using the "Doobie Brothers" name in advertising; and so the three guys ended up burning their bridges with a band generally known for maintaining good relationships with former members. Even sadder, two of the three died during the next few years.