I've noticed that it seems like none of Christopher Cerf's contributions have been included on the set. I don't know when he began working on the show, but I think it was early on. I don't think any of the songs that he provided voices in are included (none of Little Jerry and the Monotones songs, where he performed Chrissy, are included, and neither are any Chris and the Alphabeat appearances, though I don't know if they had any other season five appearances besides Count it Higher). I don't know who wrote every song, so it's possible that some of the sngs he wrote are included (then againb, he specialized in rock music, and I don't think any rock and roll songs are included in this set) I wonder if this is a coincidence or deliberate (well, it's more likely a coincidence if none of the songs he worked on were in the episodes included, but I'm not sure about songs for bonus features). A lot of songs that he wrote and performed in have been released on video and DVD in the past (witht he most recent video production to feature performances that used his voice being 2004's What's the Name of That Song?).
It's also a bit odd that Roosevelt Franklin only appears in a few cameos, and none of his starring roles are even included as bonus features. I know that he makes one brief speaking appearance, though I don't know if Matt Robinson voiced him there or not (on the Golden Age Cartoons forum, somebody said that Jerry Nelson took over the role). Regardless of voice, I don't think it would be a residual issue, since Matt Robinson apears as Gordon. I would be surprised if the DVD producers could get the legal ability to feature Matt Robinson and Loretta Long as Gordon and Susan but not Roosevelt Franklin and his mother. I would be surprised if Sesame Workshop was concerned about whether they are negative stereotypes, since some of the skits starring Roosevelt were shown on Noggin (I know that the season six premier has one of his starring roles, so if volume two focuses on the season 6 through 10 premiers then we'll probably see him more prominently). Of course, this set has the unedited version of the over, under, and around skit from the first episode, which Noggin cut to remove the black kid doing dumb things, possibly because it could be seen as racist, and that would probably be more likely to offend african americans than a major role for Roosevelt Franklin.
It's also interesting that Professor Hastings is not included on this set, and he also wasn't seen on Noggin. I wonder if Sesame Workshop really hates him (then again, I've read that his skits are frequently broadcast in non-u.s. versions of the show).