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Hogwarts School of Witchcraft and Wizardry challenge [Art] - cousin, chimpanzee, faint
Comparisons
Harry always did think that Dudley was like a monkey especially with the entire 'monkey see monkey do' concept. Except Dudley usually just 'saw' and the scratched his head with the 'do.' Maybe that made him more of a chimpanzee, especially with his size and figure.
Harry himself often went along with the Dursley's act of them not knowing each other mainly because he was too embarrassed to call Dudley his cousin. Despite the Dursleys technically being his family and putting a roof over his head, he tended to view them as something akin to a rash, damn irritating and always standing out like a sore thumb trying to blend in with the rest of your skin.
That even worked once you consider the fact that both Dudley and Vernon go red in the face and begin to huff and puff by the time they have walked down the street.
Although Dudley could just as easily be a pig with the constant stench that radiated from his room, that stink had always sent Harry to the point near on fainting. Harry reckoned that Dudley would probably be able to defeat Voldemort himself if he managed to get Volemort in his room that is. Imagine that shame, the Dark Lord Voldemort defeated by a muggle!