One of the few PAL games to be distributed in a cardbox. This was most likely done to speed up the rather large distribution of the game and to cut on costs, as the cartridge does not fit with other cases
This was the first game that was designed to be hooked up to other games. You could hook it up to Sonic the Hedgehog 3 to expand the gameplay and add new characters to play with. You could also hook it up to Sonic the Hedgehog 2.
Tails does not appear in this game, however his picture is on the spinning sign at the end of Act 1 of each level (if you pause the game at certain points).