Ghost Bride / Gerald v.s. Jamie O. - S5-E21
Corrected entry: The boys get locked in the cemetery by Helga so she can prank and scare them. Problem here is surely cemeteries lock up by a certain time, so it would've been locked before they arrived.
New Bully on the Block / Phoebe Breaks a Leg - S5-E5
Corrected entry: After Phoebe puts hinges on her cast and Helga and Phoebe are in the library. After Phoebe gets away from Helga and hides within the library shelves, she opens her cast and starts scratching her leg. When Arnold sees Phoebe he says to her, " I just saw you open and close your cast." Yet Phoebe never closes her cast.
Correction: He was just trying to say her cast couldn't be real and was also thinking of the fact that if she could snap the cast open she can snap it shut too. Any human in real life might say "open and close" when all they saw was the cast getting opened.
Parents Day - S5-E6
Corrected entry: In the first scene where she's shown, Harold's mother is a brunette, but after that she has her normal brownish hair color.
Correction: This entry seems somewhat silly, as brunette means brown hair.
Bag of Money / Principal Simmons - S5-E4
Corrected entry: Iggy removes his sunglasses - twice.
Correction: The first time he is holding his glasses there was time for him to remove them we just did not see it. The second time we see him remove them.
Corrected entry: Arnold somehow does not see the huge plate of chocolate pudding that Helga put on his chair before sitting down. (00:04:13)
Correction: Plenty of people don't look before sitting down. I once had someone put a pin on my seat in school and I didn't see it.
Correction: Not all cemeteries open and close at the same time.
That is very true. It should also be noted that not all cemeteries have overnight security or padlocked gates. So even if the cemetery was closed, the kids could still get in if this was a cemetery that isn't heavily surveilled.