Bowser In The Sky is replaced with the Bowser Gauntlet, where you must play all three Bowser stages in a row and then fight the final Bowser. If you've played BAZR, it's pretty similar to that.
You're given both keys by default, and BitDW and BitFS are inaccessible from their normal areas. You can also disable Gauntlet Checkpoints for a tougher experience- if you die at any point in the Gauntlet, you have to try again from the beginning!
Not compatible with rom hacks, but it IS compatible...
