Marf is Robot and Monster's pet, an adorable Mechanical animal who is essentially a block of metal with wheels. He acts similar to a dog and the only word he utters is 'Marf'.
Marf is a cube of metal with tiny wheels nearly hidden underneath his exterior. His facial features consist of slightly small beady eyes and thin line lips. Whenever he is angry, it is shown he has sharp teeth.
- In a promo, it is shown he can get ferocious and reveals his sharp teeth.
- He bites when angry, as seen in the episode Doctor? No!.
- Whenever he rages and shows his teeth, he resembles Domo
- If he bites somebody, he or she will get robies (a spoof of rabies).
- He resembles an electric pencil sharpener.
- He also resembles a rectangular toaster.
- The only episode in which Marf spoke actual words was on Speak Marf Speak (but that was only because Robot placed an invention on Marf).