Rifle is a female Little Penguin (Eudyptula minor; also known colloquially as "Blue Penguin") that lives at the Shipshape Aquarium. She carries a backpack of flyers for the "Swashbuckler Spectacular" show and is also the mother of Sniper.
Rifle, who is a member of the Blue Penguin species, has a number of anatomical inaccuracies: her feet are yellow instead of pink (likely changed to make her stepping in pink paint more obvious), her beak is yellow rather than dark gray-black. These anatomical differences were actually intentional. The final design document for Rifle has the following notice: "The species is called the "Blue Penguin". This isn't their actual coloration, but please make the body blue and the beak yellow." Rifle also appears rather tall for an average Blue Penguin; Rifle's design document lists Blue penguin characteristics, and describes adult Blue Penguins as reaching heights of up to 40 cm. This Is likely how tall Rifle is intended to be.