You add Hamster and Hippopotamus.Hippopotamus+Hamster. If it does not work try Hamster+Hippopotamus.
mink+chinchilla
Android+bee
Human and shark
Kangaroo and guppy
Bat+alien
Ant + Eagle
Bear + snail
Raven + dove
Dwarf+segacious
Horse + manul
Ant + Scorpionfish
Shrimp + vampire