Filch is of course a squib, someone born from a magic family but with no magical powers of their own. But that doesn't stop him inflicting punishment on rule-breakers at Hogwarts, including Harry and his friends, with the help of his trusty cat Mrs Norris.
Now, Harry Potter fans have taken to Reddit to discuss one unusual plot hole in the series - and we can't believe we never asked this question before.
After the original post asked other users to list the their unpopular opinions about the franchise, the first Reddit user who responded wrote: "Filch's position is actually insane though - the one dude who can't do magic needs to physically mop this giant castle? the f*ck Dumbledore?
"I know the house-elves are there and he's probably more of a supervisor than anything else, but we do see him physically cleaning at least once."
Filch undertakes most of chores and fixes things at the school of witchcraft and wizardry despite being unable to use magic to make these tasks much easier.
Another Reddit user responded: "Ikr! The end of DH part 2 where they show Flich trying to sweep away the tons of debris really just makes me feel sorry for him."
While a third fan mentioned the role of the house elves and their need to stay out of site. "I've always headcannoned that Filch cleaned if necessary during the day so that the house elves could stay out of sight. After all Harry doesn't even know about their existence until book 4."
We won't ever look at Filch the same after this!