At the beginning, when Jimmy O'James finds Slappy in his dummy case, Slappy is lying flat on his back and with his head facing forward. In the following close-up shots, however, Slappy's head is turned to his left side.
When Slappy is sitting in Jimmy O'James' room after their live performance, he is sitting up straight with his back to the wall. In the next shot, Slappy is seated but leaning against the wall. A few moments later, when Slappy is seen again, he is again sitting up straight.
Jillian takes Slappy's case back to Jimmie O'James and discovers that Kevin the dog was inside the case instead of Slappy. Kevin had disappeared during the previous night and Slappy was found in Jillian's bedroom afterward. How could have Jillian not known Slappy wasn't inside the case?