https://scifi.stackexchange.com/questions/28690/in-the-original-airing-of-the-pilot-was-nibblers-shadow-drawn-under-the-desk-i

My memory was that it was always there - I never had the dvds as a kid but taped all the episodes when they aired, but have rewatched the dvd versions many more times by now - and it seems that others are saying the same.

Unless the brainspawn have got to us too....