Near the beginning of the episode where the class is seen chatting amongst themselves, in the original Japanese, there was no clear dialogue, unlike the English dub, where audible conversations can be heard
Episode 4 - During the contest when comparing bust size, Ayaka is disappointed to lose to Chizuru, but seeing how they are roommates, Negi would have been bunking with them regardless who won
Episode 8 - During his fight with Evangeline, he loses his staff off the bridge and though it should still be within view in certain shots, it's gone one moment and back the next
Episode 10 - At the end of the dodgeball episode, the manga and anime endings vary. In the manga, after being stripped by Negi's sneeze, the high schoolers run off, but in the anime, instead the character Eiko and Ayaka begin talking and swooning over Negi together
Episode 14 - When Camo sees the phone on the table, he says it's Konoka's, but this is a mistake for the English dub. It's actually Asuna's.
Episode 16 - In the end credits, in the English release, Kaede Nagase's voice is credited to Caitlin Glass when it's supposed to be Clarine Harp
Episode 23 - Asuna's calandar, which reads Wednesay, October 22, 2003, is actually accurate to the real-like date. However, the series aired in 2005
Episode 23 - Asuna's birthday is on a different date than it was in the manga