Simon Simonson is a scientist who lost the chance to send his experiment into orbit to Velma Dinkley.
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Appears to be good-natured, but showed his true colors when he was the Astronaut Ghost stopping Velma from sending her project into orbit, claiming because of her, his experiment couldn't in the first place.
A Pup Named Scooby-Doo
He dressed up as the Astronaut Ghost to sabotage the shuttle launch preventing Velma's experiment from going into orbit, all because his didn't, "because of her" as he proclaims.