Real world article
(written from a production point of view)
Monster was an orange tabby cat that portrayed Spot on Star Trek: The Next Generation beginning with the sixth season. While Monster was the "more spunky" cat, Brandy, Bud, and Tyler are the other cats that played Spot. Monster can also be seen in early scenes of Star Trek Generations when he jumped on Data's table.
Monster was 'interviewed' in Star Trek Monthly issue 14. He 'noted' that the change in Spot's appearance was due to "prosthetic make-up". Monster was trained by Rob Bloch and Karen Thomas-Kolakowski of Critters of the Cinema.