From a Zep web site on hidden footage on the DVD:
I have found some footage that is a bit different than the menu screen stuff that people have been talking about on this list. Sorry if this is old news, but I figured I would put the call out.
Easter Egg spoiler***
I figured I would give the heads up on how to find them just in case anyone wanted to go right to them.
go to the Madison Square Garden Menu on disc two. Go to The Ocean, rock out til the end of the song (you can fast forward, but why when you can rock out to it). After the song instead of going into the Earls court stuff it does something else. Repeat this with stairway on the earls court stuff to find another.