When Abbott unfurls the newspaper to look for the pictures of the dead Dr. Zoomer, it is apparent that there is no printing on any of the interior pages; all the sheets are blank white.
After Bud and Lou switch burgers in the cafe, Lou eats the medallion in pieces yet, when he's X-rayed later, the medallion is intact.
While the boys are digging the hole, and after Lou has disappeared; Abbott sits down in the same place. Abbott is tipped backward, head first through the wall; but when he falls into the room below though a small hole in the ceiling; he comes through feet first.
Upon returning to Dr. Zoomer's home, Bud and Lou are wearing Egyptian robes. But after encountering Madame Rontru's henchmen, the boys go back to sporting the pith helmet costumes they wore during their first visit.
Freddie tapes his threatening voice, then puts down the microphone - but in the following shot, he's holding it again. (00:26) - "A." Oops!: Movie Mistakes That Made the Cut, by Matteo Molinari and Jim Kamm, Citadel, 2002.
Bud and Lou play back recordings on Dr. Zoomer's reel to reel tape recorder multiple times, but they never once rewind it.
When Dr. Zoomer is recording his entry at the point he says 'look there' and is killed he gasps quietly. Yet later when Costello plays back the recording at the point where Dr. Zoomer says 'look there' and is killed there's a loud scream on the recording instead.
Though Bud Abbott's character in this film was named Peter Patterson and Lou Costello's character's name was Freddie Franklin, they addressed each other by their own, real names ("Heeeeey Abbott!") throughout the picture. The credits are the only place where their characters' names are used.
Towards the end when all three mummy are running around, Abbott reaches back and says " come on Costello" instead of using his character name of Freddie.