There are, of course, shows like Fear The Walking Dead and The Walking Dead that have prequels with some minor intersecting characters.
As Young Sheldon and The Big Bang Theory are running simultaneously, there should be plenty of opportunities moving forward to criss-cross and interplay in ways that other shows can’t.
There is also Better Call Saul and Breaking Bad, but the former only hit the airwaves after the latter was finished in that case.
During the panel, the writers also mentioned that there haven’t really been two major television shows where the writers can write to the characters in “different stages of their life.”