In the Omnitrix

Inside the Omnitrix where The Aliens live and hangout before Ben Selects them Aliens (Species name in brackets):Lodestar (Biosovortian) Spidermonkey (Arachnichimp) Cannonbolt (Arburian Pelarota) Bloxx (Segmentasapien) NRG (Prypiatosian-B) Water Hazard (Orishan) Terraspin (Geochelone Aerio) Armodrillo (Talpaedan) Shocksquatch (Gimlinopithecus) Heatblast (Pyronite) Clockwork (Chronosapien) Gravattack (Galilean) AmpFibian (Amperi) Jury Rigg (Planchakule) Grey Matter (Galvan) Nanomech (Nanochip) Diamondhead (Petrosapien) Echo Echo (Sonorosian) Rath (Appoplexian) Crashhopper (Orthopterran) Alien X (Celestialsapien) Eatle (Oryctini) XLR8 (Kineceleran) Arctiguana (Polar Manzardill) NRG (Prypiatosian-B) Stinkfly (Lepidopterran) Wildmutt (Vulpimancer) Ball Weevil (Plasmasectoid) Humungousaur (Vaxasaurian) Big Chill (Necrofriggian) Wildvine (Florauna) Walkatrout (Ickythyperambuloid) Mole-Stache (Combisapien) Pesky Dust (Nemuina) The Worst (Atrocian) Kickin Hawk (Poltrian) Four Arms (Tetramand) Ripjaws (Piscciss Volann) Way Big (To'kustar) Goop (Polymorph) Swampfire (Methanosian) Feedback (Conductoid) Perk Upchuck (Perk Gourmand) Murk Upchuck (Murk Gourmand) Toepick (Terrorvian) Astrodactyl (Pterosaurian) Eye Guy (Opticoid) Snare-oh (Thep Khufan) Bullfrag (Incursean) Frankenstrike (Transylian) Buzzshock (Noseedenian) Upgrade (Galvanic Mechamorph) Ditto (Splixson) Atomix (Prypiatosian-A) Ghostfreak (Ectonurite) Blitzwolfer (Loboan) Gutrot (Gasnoid) Whampire (Vladat) Chromastone (Crystalsapien) Snakepit (Sephernoid) Sandbox (Granularin) Shellhead (Testudinoid) Fasttrack (Citrakayah) Jetray (Aerophibian) ChamAlien (Merlinisapien) Overflow (Cascan) Gax (Chimera Sui Generis) Shock Rock (Fulmini) Slapback (Ekoplektoid) Surge (Xerge). You can Be any alien you know from the Franchise or make up your own