Franchise movies have crossed over for over a hundred years, however despite the long and serialised nature of TV, they're still relatively uncommon besides spin-offs. Crossover episodes between shows indicate both shows take place in the same universe, and long running shows often have multiple over their course.

So my question is: If you take all the crossover episodes of a TV show, and combine it with every crossover episodes from that show (et cetera), how many shows comprise the biggest universe? As "crossover" is quite vague on its own, I'm imposing these definitions on it:

• The episode takes place at the location of one or both shows
• The episode features at least one character from the second show, played by the same actor.
• Parodies of a show featuring a cameo by an original cast member do not count (e.g. Saturday Night Live and Breaking Bad)
• Movies don't count as episodes

For example, The CSI-Verse:

1. CSI and CSI: Miami in Cross-Jurisdictions
2. CSI: Miami and CSI: NY in Manhattan Manhunt
3. CSI and CSI: New York in Hammer Down
4. CSI and Without a Trace in Who and What

There are additional crossover episodes within the shows, but only unique shows count here, so this is 4. Though soon it will be 5 as the CSI episode Kitty has been commissioned for a full series.

Due to the ongoing nature of TV, no definitive answer is possible, so just post whatever universe you can connect together, one universe per post.