New Super Mario Bros 2: sort-of-completed

I've seen the credits, at least.  It feels a little bit of a letdown to see the end of the game and know that there is so much still to explore.  After defeating Bowser (which I did last weekend, but never got around to writing about), I've been exploring some levels where I think there may be alternate exists based on the positioning of level markers on the map.  I've found a few, including the exit to the cannon on World 1 which leads you to the mushroom worlds.  These are a little trickier than the main numbered levels, but not massively.

I'm now exploring levels for more secrets, and trying to get enough star coins to unlock the star worlds.  From what I wrote about the original game, it looks like I'm pretty much where I called the game 'completed' last time, but the ennui's not set in yet.  Let's explore some more.