In the pilot episode The Magic Bag, not listed on IMDB, when Felix is captured by the tractor beam, his yowl is out of sync with the picture. This has been corrected on the DVD. See more
Felix the cat, / The wonderful, wonderful cat. / Whenever he gets in a fix / He reaches into his bag of tricks. / Felix the cat, / The wonderful, wonderful cat. / You'll laugh so much your sides will ache. / Your heart will go pit-a-pat, / Watching Felix the wonderful cat.