The idea behind alternate realities that are based on the little choices we make may be reminiscent of something like Back To The Future or Groundhog Day; both movies which are among my favourites. Sliding Frasiers is a finely written episode that looks at how Frasier and his world can diverge from one point, into two hilarious paths. It looks at the very extremes of Frasier's personality: happy, in-love Frasier & sad, solemn Frasier. The sub plot also mixed very well. Niles' plan of going away with Daphne goes awry in one path. What's worth mentioning here is the fact that Martin's world does not change at all; he is a creature of habit!
Overall a very enjoyable episode