It looks like my thread has been completely hijacked.
Oh well, I have only myself to blame. I shouldn't have said anything about the poobala site or about my unorthodox 2-crossovers-required rule.
In defence of my opnion, ff a crossover happens only once, then it's only a gimmick or a joke, especially if it only happened in one scene. I'm thinking of Ray Barone appearing in The Nanny, Kramer appearing in Mad About You and one of the Ghostbusters appearing on Casper. The average viewer is likely to forget that such a crossover happened, and the two TV shows will go their separate ways, free to contradict each other or even refer to each other as fictional TV shows.
If there are two crossovers which happen more than a year apart, then the producers take seriously the idea that two shows exist in the same universe and the average viewer is more likely to notice.
To put it another way, the first crossover introduces the idea that two series might exist in the same universe and the second crossover confirms that idea.
As for my real topic being too limited, not all topics are designed to inspire heated debates. Some are just simple questions that require simply answers.
I started a crossover discussion a while ago here: