After getting recently released once again as a Xbox Backwards Compatible title, Sonic Generations "Casino Night Pinball" is now free on Xbox platforms. This DLC pack is a remodel of the classic level into the style of a Pinball game. Once downloaded this 57.65 MB addition can be found in-game just before Sky Sanctuary in the black brick section appearing prior to the first boss. It's easy to access and a fun side game to play. Note that no Xbox Achievements are added with this and it's purely a fun little extra to enjoy while playing the game. This content is available for Xbox 360 or Xbox One consoles.
This isn't a large addition to acquire and worth it if you want some fun Pinball action. Might as well grab the license as it doesn't cost anything and that there are no details on how long this will last. If it follows other similar Xbox Backwards Compatible titles then it's most likely permanent. It's also worth noting that the game is Xbox One X enhanced making it look sharp in 4k resolution and it's still a blast to play.