Dood gives a postgrad course right here:
What you see is what we show you by Ken Levine
…Ken, what do you think of series crossovers, like CHEERS/WINGS? This effectively makes CHEERS, WINGS, THE TORTELLI’S and FRASIER exist in the same universe as one another.
Do you think, despite it being an obvious ratings ploy, that it’s nice to have this shared universe among the characters?
On a similar note, what do you think of the CHEERS/FRASIER episodes?
I always like crossover episodes. It’s fun to see characters from different shows interact. I especially liked the CHEERS/FRASIER crossovers because David and I wrote most of them. (Four with Lilith, one with Sam, one with Diane.) We also wrote the WINGS episode with Frasier and Lilith. Here’s a piece of totally useless trivia: David and I are the only writers to write Frasier Crane in three different series. I think that’s our legacy.
Crossovers can get sticky however, if both shows aren’t from the same creative team. On ALMOST PERFECT we did a crossover with CYBILL. There must’ve been four drafts that ping-ponged back and forth between our writing staff and theirs.
Read it all (including more about crossovers and the whole bit about directing)
While we’re at it, maybe Ken will deign to acknowledge us – or, at least TVWriter™ – after he hears that we’ve told you to buy his book, The Me Generation, because it’s great! Because it is!