A brawl with Robotnik, set on the chaotic field of a pinball table.
However, when it actually hit production, the end result was far less satisfying. For starters, it's not even really a boss, instead, it's merely a climb up a pinball table. It's either a boss that will give you some random luck, which will send you flying right to the top of the map and bring you victory in the first minute, or one that will endlessly infuriate, lasting around 5 minutes, as you continually reach the top and get betted down time after time, thanks to the messed up pinball p-hysics of Sonic CD. Like I said, it had potential to be fun, but ended up just being a mess.
So the question is, what other bosses can you think of that had great potential but ultimately failed?