Growler is a depiction of a futuristic muscle car shaped like a dog. The spikes on the engine and sides are meant to resemble a collar and the toothy grille is meant to resemble a mouth. The casting was changed in 2016; the base was changed slightly with the rear rivet's position being moved.
From the back of the 2012 card:
Born: 2011
Birthplace: El Segundo, CA, USA
Designer: Hot Wheels®
Specialty: Choke-collar styling on the roof and sides along with a vicious front grille and bone-shakin' V-8 engine, make this canine-inspired muscle car one bad dog.