Futurama's Oldest Mystery SOLVED: Was Nibbler's shadow in the FIRST AIRING of Space Pilot 3000?
Interesting video I saw on YouTube which definitively shows whether Nibbler’s shadow was in the original airing of the pilot. Skip to 23:50 for the answer.
They did a minor retcon later. The scene is shown again and as well as the original shadow (And nibbler's eye in the bin), you see Fry's shadow too, since he time travels back there in the Why of Fry. Unfortunately I can't remember which episode this is in at the minute