I did have a vague idea for a followup, but probably involving Batman rather than Clark.
The trouble with this thing now is that with 116 (I think) authors and 250+ chapters an awful lot of ground has been covered, some of it by (dare I say it?) less than inspiring authors. Reading through all that to find out if an idea has been used or not is a fairly lengthy business.
I think that the guy who started the story has acknowledged the influence of the Callahan's Bar setting - it'd be difficult to pretend ignorance given how many people have "borrowed" the idea over the years - and it was hardly original with Spider Robinson in the first place...
