I think the theme is nice and it works. The setting is interesting the cat vs dog has not been explored to death but its not unknown so there is tons of material and jokes to draw from. Tons of cat vs dogs jokes can be told.
I feel like the game type has been done over and over again. The style of the game goes all the way back to Space Invaders. I have not seen what special thing do you bring to the table? Games like The Last Stand brought items and upgrades and strategy to the game type. Why is your game different from all other sidescrolling shooters?