Simon Bar Sinister is the main villain in Underdog. In the 2007 live-action film adaptation, he is portrayed by Peter Dinklage. In the movie, Bar Sinister was originally a geneticist for a company in Capitol City, using dogs as test subjects for the betterment of mankind. But after being laughed at by the Mayor after attempting to have his research expanded to law enforcement, Bar Sinister began his work to create a super-power formula to get revenge. Soon his loyal dogs betray him after realizing Simon's treatment on them. The incident resulted in the destruction of his lab that not only scarred his forehead, losing some of his hair, and being limped in his right leg, but created Underdog. Simon Bar Sinister is sent to jail for all his crimes.

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