
There's more of these than you'd think.
Earth is a planet literally teeming with organic life forms. Millions of genera, of all shapes and sizes, inhabit the planet, and aCybertronian might scan any of them for a potentialalternate mode. Some genera, however, are extremely popular with Cybertronians.
Transformers Wiki has certain requirements for an animal to be listed here. There must be at leastthree unique toy molds (or in-fiction appearances, in the case of non-toy bodies/characters) that share thebeast mode. There must also be at leastone unique character per mold—a single character getting numerous revamps in similar bodies over the years would not count as a "popular mode."
Each mold is listed on its own line, with all different-character decoes/retools on the same line. The list is (more or less) organized in chronological order of toy release or fictional appearance.
- See also:Popular Earth vehicle alternate modes,Popular Cybertronian vehicle alternate modes,Non-vehicle non-beast alternate modes,General Motors
Arthropods
Arachnids
Spiders
Black Widow Spiders (Latrodectus mactans)
Scorpions

Willing to trade his bee for a city mode.
Crustaceans
Crabs

When all the world is metrosexual, the Crab People will finally reign supreme!
Insects
Stag beetles (family Lucanidae)
Scarabs and male rhinoceros beetles (family Scarabaeidae)
Grasshoppers and locusts (order Orthoptera)
Wasps and ants (order Hymenoptera)

A rare shot of Waspinator not getting blown up.
Mantises (order Mantodea)
Dragonflies (order Odonata)
Fishes
Chondrichthyes
Rays
Manta Ray (Manta birostris)

Starring in the next
Shark Attack movie.
Sharks
Hammerhead shark (genusSphyrna and others)
Great White shark (Carcharodon carcharias)
Reptiles
Crocodylians

Don't flush him down the toilet.
Lizards
Snakes
Cobras (genusNaja and others)
Turtles
Snapping turtles (generaChelydra andMacroclemmys)
Dinosaurs
Ankylosaurus
Brontosaurus[5]
Pachycephalosaurus
Spinosaurus
Stegosaurus

"
Slag stole my name." :'(
Styracosaurus
Triceratops
Tyrannosaurus

"Down, Dino. Down, boy! Down, boy! Down!!"
Velociraptor
Pterosaurs
Pteranodon

Won't you, take me, on your mighty wings...
Birds
Condors (generaVultur andGymnogyps)
Eagles (order Accipitriformes)
Hawks and falcons (order Falconiformes)

It's a bird! It's a plane! It's both!
Owls (order Strigiformes)
Synapsids
Dimetrodon
Mammals
Bats

He tried to get a recurring role in
Batman Beyond.
Bovids

Not a Terror dog, we swear.
Canines
Wolves / Dogs (Canis lupus)

Timber from
G.I. Joe Crossovers...if such a toyline existed.
Proboscideans
Equines
Felines
Jaguars (Panthera onca)
Tigers (Panthera tigris)

Tigertron after visiting a tanning salon.
Lions (Panthera leo)
Cheetahs (Acinonyx jubatus)
Primates
Gorillas (Gorilla gorilla)

Could 100 humans take
him on?
Humans (Homo sapiens)

"I'm not an animal! I'm a
human being Pretender shell!"
Rhinos

Just when you thought a rhino's skin couldn't get any tougher...
Rabbits
Rodents
Rats
Ursines
Bears (genusUrsus)
Mythical creatures

Moonlights as a Yu-Gi-Oh! card.
References