Movies are converted for DVD in Europe at 25 frames per second instead of 24 frames per second, resulting in a 4% faster playback of the same movie. This makes the sound higher-pitched, and can reduce animation quality by adding 'ghost frames.' The Rainbow Brite release used the PAL version, so even though it's Region 1 it still has the speed-up.
The same issue has been happening with Filmation releases lately.