I wondered that there still no topic about this crossover. Cause mod's creator even copied structure of some Super Meat Boy levels. Well, MeatyMod is game with Aquaria's mechanics and SMB's difficulty (and as I heard, Super Meat Boy has "almost impossible" difficulty, but still didn't play it). What it has for now:
* 40 regular maps
* 5 extra hard bonus maps (WAAAAAARP ZOOOOONES - Can you find them?)
* 12 additional maps (transition, beginning, and ending maps)
* 1 bonus form, replaces fish form
* 4 Bonus items with very helpful effects.
* Auto-recording and playback of replays (saved along with the game)
* Save anywhere (Press ESC on a level map to open a custom menu where you can save, among other things)
* Lots of hazards, including, but not limited to:
+ Saw blades, Saw blade shooters
+ Missile launchers
+ You don't really want to know
* The good old jumping physics from Aquaria that everyone loves!
* And there is cake!
I recorded some gameplay: http://www.youtube.com/watch?v=mjzXa_5t4Bw
Main MeatyMod topic here