Teresa: If you put in a rocket ship it becomes SF, and can only be turned into fantasy by introducing the holy grail. "The holy grail in the form of a rocket ship is the Hugo."
We get into a discussion of what defines different genres--interesting because it's not all on the same spectrum. Bear thinks of SF as the literature of testing to destruction. This explains a lot. More generally, SF and fantasy are defined by the speculative element. Horror and humor are defined by the emotional effects they attempt to produce. Most other genres (e.g., mystery) are defined by specific plot elements. SF and fantasy play well with others, because you can combine their setting and ideas with borrowed plot structure. But Jo points out that to pastiche any genre, you have to love it.
The whole thing..