*SPOILER ALERT* The TV show St Elsewhere takes place inside the mind of Tommy Westphall. All TV shows that crossed over with St Elsewhere, and all shows that crossed over with those, are Westphallian.
Direct crossovers have been connected to St. Elsewhere. Those in the secondary category are connected to those in the direct category. And so on. I went with the source, even where the connection is spurious. For example, Yoyodyne is a common gag name for a company, but the source treats it as a legitimate link. Oppositely, cartoons are ignored, even where the connection is clear.