Yes, Ben 10 initially has 10 aliens that he can transform into using the Omnitrix.
The Original Omnitrix Set
According to a reference regarding the Ben 10 series, it is explicitly stated that "There are 10 aliens in Ben 10." These initial transformations are the core set that Ben discovers and utilizes at the beginning of his adventures.
Meeting the First Aliens
The reference confirms the existence of this specific number of alien forms available to Ben from the outset. One example mentioned is Forearms (often spelled Four Arms), a powerful quad-armed alien. The concept revolves around Ben discovering and learning to master these distinct alien abilities.
This foundational set of 10 aliens is central to the premise of the original Ben 10 series, allowing for a variety of powers and scenarios as Ben battles villains and solves problems.
