Pepsi is Marcus' mean and hateful wiener dog. The dog is often refered to as "Pesi". This dog is famous for constantly humping Liam or the other dog in the household, Pepper. Although both Pepsi and Pepper were perhaps the worst dogs ever, Marcus never missed a moment to kiss them, hug them, or shower them with love. Adam and Liam secretly wished Marcus would forget to feed them so they would die.

It is distinguishable from Pepper by its short hair.