A few ideas: a bonus to jumping and catching coins and ammo.
Allow for doing a slow motion zoom in back flip to catch coins and ammo.
Allow birds to poop on you if you get underneath them.
Enable dogs to bite you and shake you around, slowing you down, making going out of the fort even more tricky. Allow for a talent tree enabling a cat double jump.
A dog siege engine might be interesting to add.
Show how much damage is increased in the weapons and base menu.
Mousing of the other upgrades don't appear over reload. On the gun options.
Having the guys with clubs have a slam stun attack.
A Giant Red dog as a final boss?
Kick back and not being able to shoot while running with the chain gun might make it feel a bit more powerful. Maybe you could have the cat city be rebuilding the town in the background, gaining progress after each level. Opening up new menu options.
One of the few games where I didn't mute the music.
I really like how you can click, drag and drop an item into your inventory and exchange it for experience right away. Might be nice to have character classes and racial abilities. Maybe dwarves could see hidden passages easier.
The game slows down about 45 min in. Not as much of a reward climax of reward sounds. Some of the mission reward sounds seem like I did something wrong instead of gaining an award. A hot key for speed up would be nice. Also flames around the fast forward key when it's on would be nice. I like the characters and cows. The level jumping man was nice. I wish I could click on the weight room and bar. Businesses have needs to. Maybe ceiling cat could invade the bar. Or the air could go out in the weight room, or the entire building. Maybe the elevators could break down. You could throw in elevator repair man as a unit you could hire.
The game has appealing graphics. But the diffiulty curve needs to be adjusted. It might be interesting to have more complex and zoomed out levels. The units seem to be a bit gimmicky. Perhaps weakening the starting units and lowering the cost of the purchased units might increase play enjoyment.
 "ROT"){kind=icon}
 "World's End Chapter 1"){kind=icon}
 "Incursion 2: The Artifact"){kind=icon}
 "GunBot"){kind=icon}
 "Utopian Mining"){kind=icon}
 "Kitt's Kingdom"){kind=icon}
 "Questopia"){kind=icon}
 "Happy Tower"){kind=icon}
 "Pixel Kingdom"){kind=icon}
 "Seeds"){kind=icon}
 "Caribbean Admiral"){kind=icon}
 "Knightfall 2"){kind=icon}
 "Ge.ne.sis"){kind=icon}
 "Bloons Tower Defense 3"){kind=icon}