Dick Wolf, David E. Kelley, Shonda Rhimes and Joss Whedon have all done it. You may be wondering what IT is exactly. They've all at some time point created a spin-off or expanded their TV show into a franchise (see Law & Order). They've all done crossovers between their shows, if you count the backdoor Private Practice pilot on Grey's Anatomy last season.

But those crossovers would not have been possible if they didn't all share one common trait: all of them are showrunners who have, in recent memory, shepherded multiple television shows, sometimes across different channels.

The ...