Floaterbots, GO!

[AimlessZealot]

So, I have been working on monsters for the roguelike game that I am doing and this is one of the critters I've made -- the Floaterbot. I intend to switch out the energy and metal casing colors and a few of the appendages based upon how they have evolved throughout the game. The four designs from left to right represent the four stages of "evolution" that the game may show depending on how much you've been killing them. Kill too many, and the next, hardier form will show up to make you regret it.

[IrresponsibleFreelancer]

Just wanted to point something out. The final bot looks like it's arms are noodles, you said they were metal at the moment so it doesn't quite make sense that they would be so flexible. ( unless that's on purpose) I believe the best way you could fix this is by choosing how you want to divide it and not bending those parts any more than is possible ( like how you can't bend the bones in your forearm). Also there are some pixel problems especially on the last bot's right arm right near its armpit. There is a part where in the second or third frame of it you have this harsh point. What I said before can kinda be ignored in order to get rid of this. The way to do this is simple. Remove that one pixel that is making it too sharp and squarish.  Other than that they look awesome and I love the idea of an evolving enemy and the way it's executed. 

[AimlessZealot]

Well, the noodle-y arms are intended to be segmented, whip-like appendages but I'm thinking that maybe I need better contrast and maybe some more clear segmentation along the edges. I'm glad that you like the concept behind them and I hope to have more to show later. I'm working on a quadruped at the moment and it's breaking my soul

[Pusty]

Well I am new to pixelart but I think it looks really nice.
I like the idea of visual changing enemies after killing too many of them