Sonic Mega Collection/Hidden content
From Sonic Retro
Removed Content
When hacking into Sonic Mega Collection, one can find the entire European Sonic CD manual. Not only that, but a preview version has Sonic CD on the list of games to pick. On the same preview version, in the movies section, you can find "Sonic the Hedgehog Movie Part 1" and "Sonic the Hedgehog Movie Part 2", likely meaning that the Sonic OVA was once in Mega Collection.
A Sonic Mega Collection prototype released by drx actually has all of this stuff included, however the movies and the Sonic CD game are nonfunctional.