No game in the Mario series was more willing to dispense with established rules than the second game in the series (yes, I know, "Doki Doki Panic", etc, etc). Of all the rules it broke, though, the most sinister was clearly the one that most of us took for granted.
What's offscreen is in the past.
|Or, more often than not... falling like hell|
He was relentless and invulnerable. The only way to escape was to drop the key (not always a good idea on those long elevator chase falls, and besides, he'll be waiting for you to pick it back up again) or get through the locked door.
Of all the enemies from SMB2 that I wish had reappeared in subsequent games, Phanto is easily number one.