well I've been having a look through these with a tile editor - there are graphics in the 50 in 1 for Inventor games that arent used, Power Boat and Skiing.. and right at the end there are 1943 graphics for some reason. Also the Finger DDR graphics are included partially up by Space Shuttle, then in full near the end. they're even there with Space Shuttle in the 60 in 1.
The 30 in 1 has two de-pokemonified games from Union Bond's Pokemon 4 in 1 - Pet Dance and Pet Slot - but the rest of the multi (its graphics at least) is hidden in there, Pica Click was renamed "Pet Click" and Pacman was renamed "Bean". Quiz has an unused title screen reading "The Way To Millionair" and what looks like a 2001 copyright.. and I'm not sure what the games are around 320000 & 336000.
and in the 101 in 1, theres yet another unused Inventor game, another Rad Racer hack from the looks of things. I guess one of the motorbike ones.