During the beginning of "The Awful Battle of the Pekes and the Pollicles," Victoria and Jemima can be seen sitting next to Old Deuteronomy watching along. In one scene, it shows them start to get up and leave, and they are gone in the next scene. The scene afterward, they are shown sitting there again, and gone again in the next.
During 'Old Deuteronomy', Mungojerrie can been see in the background lying in front of Rumpleteazer with his head on her lap. The film then cuts to a close up, in which Mungojerrie is now lying *behind* Rumpleteazer, propped up on one elbow. When the film goes back to a long shot, Mungojerrie is back to his original position. In some shots, Mungojerrie and Rumpleteazer disappear entirely.
During the last part of "The Gumbie Cat", we see Munkustrap, Jellylorum, Demeter, and Bombalurina helping Jennyanydots take off the Gumbie costume in the front right part of the stage. We see her in her flapper outfit, then there's a shot of the beetles, and in the next shot, Jennyanydots is in the center back of the stage, walking forward, and the others have disappeared.
In the Macavity song with Demeter and Bombalurina, Demeter's left legging changes from being pulled up or down by her ankle between shots.
At 1:12:03 the camera and boom can be seen in the lower left.
The poem/song "The Naming of Cats" states that a cat's "second name," such as those used by the characters in this show, is unique and not shared by any other cat. However, the song introducing Old Gus the Theatre Cat says that his full name is Asparagus, which is also the name of another cat in the show. This is because John Mills, who played Gus, was unable to do the rest of the singing and dancing the role required, so the character was split into two identically-named characters.