When arriving on Earth, there are millions of animal species a Cybertronian might scan for an Alternate mode. Some genera, however, are extremely popular with Cybertronians.
- (NOTE: For the sake of saving space, characters on this list who share a toy mold are combined into a single line.)
Arthropods
Crabs
Scorpions
Generation 1/Beast Era
- Double Punch (G1)
- Pincher
- Poison Bite
- Scorpia
- Scorponok (G1) / Black Zarak
- Scorponok (BW) / Sandstorm / Double Punch (BW)
- Scorpulator
Unicron Trilogy
Transformers (2007)
Dinosaurs
Tyrannosaurus
Generation 1/Beast Era
Unicron Trilogy
Animated
Triceratops
Generation 1/Beast Era
Unicron Trilogy
Animated
Stegosaurus
Generation 1/Beast Era
Unicron Trilogy
Velociraptor
Generation 1/Beast Era
Unicron Trilogy
Pterosaurs
Pteranodon
Generation 1/Beast Era
Unicron Trilogy
Animated
Dragons
Generation 1/Beast Era
- Megatron / Cryotek
- Deathsaurus (partially)
- Galvatron (BWII) / Unicron
- Nightscream (Classics) / Dragoyell
- Savage
- Snapdragon
Robots in Disguise
- Megatron/Galvatron (partially)
Unicron Trilogy
Mammals
Bats
- Mindwipe
- Nightscream
- Optimus Primal / Onyx Primal
- Ratbat
- Skar / Clouder
- Sonar
- Soundwave
- Batbreast
Carnivores
Bears (genus Ursus)
Canines
Wolves / Dogs (Canis lupus)
Generation 1/Beast Era
- Carnivac
- Wolfang (Maximal) / Wolfang (Predacon) / K-9 / Max-B
- Weirdwolf
- Sixshot (partially)
Unicron Trilogy
Felines
Jaguars (Panthera onca)
Tigers (Panthera tigris)
Lions (Panthera leo)
- Angela / Dark Eggleo / Eggleo
- Lio Convoy
- Leobreaker / Nemesis Breaker
- Lionbreast
- Leonicus
- Prowl / Lio Junior
- Razorclaw
- Snarl / Alpha Trion
- Steeljaw
- Under-3
- Victory Leo
Pumas (Puma concolor)
- Pounce
- Quickswitch (partially)
Cheetahs (Acinonyx jubatus)
Sabertoothed cat (Smilodon sp.)
Odd-Toed Ungulates
Rhinos
Generation 1/Beast Era
- Headstrong
- Ramhorn
- Rhinox
- Stranglehold
- Greatshot (partially)
- Rhinobreast
- Top-Heavy
Unicron Trilogy
Primates
Gorillas (Gorilla gorilla)
Generation 1/Beast Era
Unicron Trilogy
Go-Go-GoBots
- Gorillabot / Beast-Bot / Gorilla-Bot