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Mr. Weasley is Ron's father. He works for the Ministry of Magic, in the Misuse of Muggle Artifacts Office. He loves Muggle culture and is fascinated by Muggle objects. This interest leads him to a surprising conflict of interest. His job is to catch wizards who put magic on objects meant for Muggles, but, at the same time, Mr. Weasley is always enchanting Muggle things. As Fred puts it:
Yeah, Dad's crazy about everything to do with Muggles; our shed's full of Muggle stuff. He takes it apart, puts spells on it, and puts it back together again. If he raided our house he'd have to put himself under arrest. It drives Mum mad. (3.53)
Mr. Weasley's interest in Muggle artifacts leads him to bewitch the car that Ron, Fred, and George use to break Harry out of the Dursleys' house. It's also this flying car that Harry and Ron drive to Hogwarts, illegally exposing their magical activities to seven Muggles on the way. When Lucius Malfoy finds out about Mr. Weasley's car, he jumps on the opportunity to discredit Mr. Weasley's work with Muggles. In the Daily Prophet, Harry and Ron read:
"Weasley has brought the Ministry into disrepute," [Lucius] Malfoy told our reporter. "He is clearly unfit to draw up our laws and his ridiculous Muggle Protection Act should be scrapped immediately." (12.164)
Unfortunately, Mr. Weasley's understandable (and really funny) obsession with Muggle things proves to be a weak point on which racist creeps like Lucius Malfoy can attack him. Lucius uses Mr. Weasley's positive feelings towards Muggles to show other pureblood bigots that Mr. Weasley can't be trusted. This profound struggle between Mr. Weasley (who likes Muggles, doesn't worry so much about money, and is kind and warm) and Lucius Malfoy (who hates Muggles and is rich, powerful, and cold) is the grown-up version of the rivalry between Ron and Draco. The mutual mistrust between the Weasley and the Malfoy families is a generational problem; we'll have to wait until the end of the series to see if there is any way that the two families can make peace.