For crossover images that make you think, "Wow, I never even considered the possibility of this being crossed over with that." Not a voice actor connection or name connection, but where the artist threw together two or more series with little in common, seemingly at random. Often results when Japanese popular culture is crossed with Western popular culture.
Although it may elicit this response, one must truly consider if there is anything Touhou wouldn't be crossed with.
Applies to parodies too.