I am very fond of this concept. It has a classic arcade feel with some fun little twists. I really enjoy the lighting, monochromatic scheme, and the cute and creepy 8 bit sound track. I also quite like the lighting dynamics. I do have a couple of critiques.
1. The control scheme isn't really all that intuitive in my opinion. I would opt for ASDF controls, with spacebar jump and click attack, given the option.
2. Slash Chicken and ratbone are very vulnerable characters. Their attacks don't invoke an invulnerability state, or prevent enemies from hitting you in any way that I can tell. Rollerpig, on the other hand, is an easy choice, seeing as for as long as you are holding attack, you are nigh invincible, and constantly attacking, while also receiving a boost to mobility. I think rollerpig was fun, so maybe only a minor nerf to his attack if any, such as certain actions breaking it, or maybe a stamina bar? The others definitely need a buff of some kind, or a defensive ability.