First off, making a block tail move side to side would look weird, at least done if done like this.
Second, have you never gotten a fake "YOU ARE A WINNER" pop up?
EDIT- Oh, and to add to the tail thing, the tail thing was also to have it match up with the fin to give it an equal machine vibe.
why does the tail move upwards and downwards? fins are supposed to move sideways, perhaps that is why I didnt even recognize it as a fish ....also the "win" just seems tacked on and doesnt remind you of an annoying popup at all
Great concept on this one, hehe. Would it help if the popup was more obnoxious? You know, give the player more motivation to kill it? 
I did that originaly and honestly, it looked odd with the bouncing whole body movement the fin would aline with the bobing making it look like the fin was sitting still. I need to learn how to work around that.). I might make an alternate version for the game animation since it's movements will actually have it go in a stright line (as in, no bobing up and down, just straight, hop out of water, land, straight).
Then again, the idea of the fins moving together like that almsot seem fitting for it, seeing as it's a computer thing, idk, maybe it's jsut me.
YOUR PIXEL WAS NUMBER 100,000!!!! THIS IS NOT FAKE YOU HAVE JUST WON $10,000!!!! CLICK NOW!!!
..nice piece! :) only crit is to maybe slightly offset the bounce of the fin and flipper?
Magicarp used Splash! "Oh Sh@#" -Ash Ketchup
I like your cubetastic style of animations =)
Diggin' these sprites. I'd like to see a whole mockup.
Come On Who Doesn't =).... But I Like this Little guy =)
how you fix it is up to you, but Bowzware, Fevirus and Weirm all look more like they'd move by swimming than this guy....who stomps like chilljan. I honestly didnt think this was a fish at all until I noticed the pun in the name...and if you have to resort to context to get the image then the image is not doing it's job.
I can see that just the tail swinging sideways wouldnt be clear, I think maybe if the fin that goes trough the body should swing sideways too, so that you can see the wave go trough the body and it's clear what's going on.
I understood perfectly the concept of "you win" popup windows, I'm just saying that a little bar on top of the character doesnt convey that, it doesnt look like apopup window but a bar, and "win" is often used to abbreviate windows so the message is further lost. I think it would be better to incorporate this idea into the design of the fish rather than just tacking an unclear bar on top.
I would suggest maybe making his eyes of flashy colors (like the popups) and put a window around the eyes. hell...even replace the eyes with flashing "u" and "win" or something?
I hope you dont take any of this as a criticism on your art as a whole or even this aproach to portray viruses...Bowzware is on my favorites and I'm watching your stuff...I just dont feel like commenting if I dont have a crit or something of substance to say :p