Cannonance has the highest base Special Attack stat of all Steel-type Pokémon and all Dragon-type Pokémon. It also has the highest base Defense and Special Defense stats of all non-legendary Dragon-type Pokémon.
Cannonance has the highest base stat total of all non-legendary Steel-type Pokémon and all Dragon-type Pokémon.
It might be a reference to how many pseudo-legendary Pokémon are Dragon-type.
Cannonance's large, gaping mouth suggests that it is based on Birdo from the Super Mario series, or possibly Robirdo or Mecha Birdo from the indie title I Wanna Be the Guy, considering its Steel type. It bears a resemblance to a cannon, and its legs resemble the wheels many cannons have. It might be based on a dog, but this is unlikely.