I’m currently adding a rather hefty extra bit to Fishbane (work-heavy, anyway! it’ll probably be pretty small when it comes down to comparing it to the rest of the game, but it’ll be worth it!), with lots of unlockable stuff from additional story (well — story at all, since Fishbane doesn’t have much of a story in its current incarnation!) to wearable skins to random related pixel art.
Here is an example of what you might find. This may be accompanied by an alternate costume for Fishbane :)