Recently I discovered that people have actually started working on Mushroom Kingdom Fusion again, after it was in hiatus for a long time. It used to be maybe my favourite fangame ever, combining all kinds of different franchises while still keeping the Super Mario Bros 3 / Super Mario World style gameplay.
The game still isn't finished but I'm surprised they're working on it at all.
Levels included in this video:
00:00 Intro
00:12 7-S4 Journey to Funkotron (Just a quick look)
02:18 Doc Robot: Revenge of the Robot Masters: The Movie: The Game
04:09 7-5 City Escape (Metal Sonic + EGG Truck boss fight)
22:25 7-9 Winged Fortress Zone (Silver Sonic boss fight)
29:01 the LAST Doc Robot finally
29:49 7-10 Lava Powerhouse Zone
43:44 7-BOSS Robotnikland (Dr. Robotnik / Eggman boss fight)