Andy's Omnitrix aliens so far...

As of right now, Andy has 5 aliens in his arsenal. Here's an introduction to them for those who don't know them or want to know more:

Split-Warp (top left) - Andy's first and most frequently used form. Split-Warp can teleport, fly, and has super strength and speed. He has a retractable fusion cannon on his right arm and retractable null rays on both arms. Split-Warp's wings can move backwards and forwards and up and down for better maneuverability, especially in tighter spaces. Ben picked this form for Andy's Omnitrix because its robotic nature makes it better compatible for Andy's nanites and easier to channel his builds through. Split-Warp is Andy's go-to alien.

Sonic Doom (top right) - Andy's second alien form, though not as frequently used as Split-Warp. Sonic Doom is big and bulky and has a more limited range of movement, making him seem stiff and extremely robotic. He has two large speakers mounted on his shoulders and two smaller ones on his headphones which can emit a variety of sonic waves that can do various things such as disrupting machines and immobilizing opponents. Sonic Doom can launch explosive cassettes from the tape deck on his chest or razor sharp CDs (similar to shuriken) from the CD slot above the tape deck. He can either launch his projectiles automatically or throw them by hand after ejecting them. Sonic Doom can transform into a boombox in order to intensify sonic waves or to hide, especially in small spaces. The antennae on his headphones (there to make the headphones look like music notes) can pick up radio waves/transmissions, making him effective at intelligence gathering. The buttons on his stomach are used to change stations/frequencies and adjust volume. Sonic Doom has a retractable laser cannon near his right shoulder and can effectively channel Andy's builds like Split-Warp, but Andy generally only uses his pile-driver build (the only original one he has) since Sonic Doom can amplify the vibrations, making them more effective. Sonic Doom is super strong and it is extremely difficult to read his emotions since his face does not move at all, save for his eyes, but the eyes have limited expressive qualities. Andy uses that to his advantage so his opponent cannot see what he is feeling.

Terrorsaur (name pending) (bottom left) - Andy's largest and deadliest form. Similar to a dinosaur, dragon, and a lizard, this form is very predatory and very violent, although the violence is very controlled for precision-sake. His behavior is similar to a velociraptor or a Tyrannosaurus Rex. Terrorsaur cannot talk, he can only growl, roar, screech, etc. He has sharp front and back claws, several razor sharp teeth for biting and tearing, and an extremely flexible body. He can constrict his enemies, similar to a snake, and can even collapse some of his skeleton to do so. Terrorsaur has heightened senses such as smell and vision and lightning-fast reflexes, making him an excellent tracker and killer. Terrorsaur can shoot balls of purple fire at enemies (like a Night Fury). When submerged in water, he adapts to a more sea monster-esque form with fins and all that good stuff, making him a formidable opponent on land and sea. He's strong enough to bite/tear through the strongest of metals, making him an effective resource for taking down large ships, armored buildings, or mechas. Terrorsaur is Andy's preferred form when he wants to be big and intimidating.

Pajaro Furioso (middle right) - Literally "angry bird" in Spanish. Pajaro Furioso is an "Angry Birds" based alien. Pajaro Furioso isn't used very often, usually just for fun or when a good ole explosion is needed. On its own, this alien can't do much, but when launched at high speeds via Rex's Slam Cannon, falling from the sky, or other means, he can slam into opponents or obstacles and destroy them with a huge explosion. The speed at which he is launched determines whether or not he will explode and the magnitude of the explosion. No harm is done to Pajaro Furioso when he explodes, at most some minor physical damage from hitting things too hard.

Conejito Grandisimo (bottom right) - Literally "big bunny" in Spanish. Andy's least used and most hated alien form because it's "pink and girly". Initially, Conejito Grandisimo is a small, raggedy-looking rabbit with spikes. When he gets angry (usually from someone calling him "cute"), he transforms into a huge, scary-looking rabbit with the attitude of Rath and the strength of Humongousaur. Andy tries his best to avoid this form at all times, preferring to use Terrorsaur for the big, strong alien. Andy is constantly teased by Dean and Sam when in this form. Andy's mother, Rex, has a strong aversion to this transformation due to an irrational fear of rabbits after being attacked by rabbit EVOs when he was younger. Ben has been accused several times for including this form in order to embarrass his son and scare the bejeezus out of his wife. Conejito Grandisimo was created by ~Punkheart11: [link]

Now that you guys know more about Andy's aliens, enjoy these sketches!

Ben 10 and Generator Rex (c) Man of Action
Sam Nixon (referenced in description) and Conejito Grandisimo belong to ~Punkheart11
Dean Salazar (referenced in description) belongs to ~bambzilla
Andy Salazar-Tennyson, alien forms, and art belong to me