Board Thread:General Discussion/@comment-98.222.188.34-20130316183702/@comment-16202203-20130822091853

I believe most people have the right idea. 57 seems to be the correct number of canon alien forms the current Ben has transformed into on screen (soon to be 59 with Whampire and Gutrot). However, there are plenty of non-canon/locked aliens connected to the series as well. These aliens are:

Eon

Spitter

Buzzshock

Atomix

Sandbox

Snakepit

Shellhead

Rocks

Squidstrictor

Portaler

Eon was only used in an alternate timeline. Spitter and Buzzshock were used only by Ben 10,000 in the future. Atomix, Sandbox, Snakepit, and Shellhead were all mentioned by Ben 10,000 in the show, but were never shown on screen. Rocks and Squidstrictor appeared only in a play called The Power of the Omnitrix, and are certainly not canon. Portaler was the winner of the Draw Your Own Alien Contest, and thus is not canon. This brings the total up to 69, or 87 with the Ultimate forms included (Ultimate Ben and Ultimae Greymatter are excluded). Thus, the answer is indeed a total of 87 aliens.

I have no idea how many other aliens are unlocked. I just assume that the aforementioned 59 aliens are the only ones Ben currently has access to.