Caillois, too, proposes as a “touchstone of the fantastic ... the impression of irreducible strangeness.”
As I'm quoting from an online excerpt I can't tell whether or not Todorov's book quotes the source of this definition (which will be important in evaluating Todorov's own theory). I did find that source elsewhere online, though:
Apparently the quote comes from a Caillois book named AU COEUR DU FANTASTIQUE, which as far as I can tell has not been readily translated to English. Todorov is apparently rejecting Caillois' definition(s) as too limited, however.
More on these matters later.