Aliens section compiled by the TAS Coordinator.

A, B  
Andorian "Yesteryear"
Aquans "The Ambergris Element"
Argo Sea Snake "The Ambergris Element"
Arretians "The Counter-Clock Incident"
Aurelans (see "Skorr") "Yesteryear"
C, D, E, F  
Caitain "The Survivor"
Capellan Power Cat "How Sharper...Serpent's Tooth?"
Cosmic Cloud Creature "One of Our Planets is Missing"
Draimians "Albatross"
Delta Theta III Aborigines "Bem"
Edosians "Beyond the Farthest Star"
G, H, I, J  
Gorn "The Time Trap"
Glommer "More Tribbles, More Troubles"
Gnalish "The Jihad"
Guardian of Forever "Yesteryear"
K, L  
Klingons "More Tribbles, More Troubles"
Kulkukan "How Sharper...Serpent's Tooth?"
Kzinti "The Slaver Weapon"
Lactrans "The Eye of the Beholder"
Le-matya "Yesteryear"
M, N, O  
Megans "The Magicks of Megas-Tu"
Motherlode Aliens "Mudd's Passion"
Nasat "The Jihad"
Orions "The Pirates of Orion"
Orion Slave Girls "The Time Trap"
Pandronians "Bem"
Phylosians "The Infinite Vulcan"
Phylosian Swoopers "The Infinite Vulcan"
Pod Ship Insectoids "Beyond the Farthest Star"
Practical Joker "The Practical Joker"
Q, R  
Questar M-17 Alien "Beyond the Farthest Star"
Retlaw "The Infinite Vulcan"
Rigellian Hypnoid "Mudd's Passion"
Rock Creatures "Mudd's Passion"
Romulans "The Survivor"
Sehlats "Yesteryear"
Skorr "Yesteryear"
Slavers "The Slaver Weapon"
Taurean Women "The Lorelei Signal"
Tellarite "The Time Trap"
Terratins "The Terratin Incident"
Tribbles "More Tribbles, More Troubles"
U, V  
Vedala "The Jihad"
Vendorians "The Survivor"
Vulcans "Yesteryear"
W, X, Y, Z