Ditto

Ditto
Ditto (voiced by Rob Paulsen) is a small, humanoid alien with the ability to clone himself without limit. Every clone operates independently, regardless of whether or not Ben wants them to, and each clone is indistinguishable from the others. Though the clones are autonomous, pain felt by one clone is transmitted to the rest, and the death of one will result in the death of the rest, as demonstrated by Dr. Animo's Ditto-enhanced Stinkfly mutants. The cloned Dittos can also merge back into an individual entity if they desire.

When the Omnitrix times out, the Ditto clones are forcibly recombined into one before the transformation reverts. If one or more clones are isolated from each other when the Omnitrix times out, however, the timer will reset and Ben won't revert back into human form until they are reunited. This only seems to apply when a clone is physically unable to reunite with the others; in open air, the clones will float to each other over great distances in order to facilitate the transformation. It is implied that the reset "glitch" forces the Omnitrix into a state where the next transformation is timed out much faster than usual, due to the strain of being active through multiple timeouts.

Though Ditto's cloning ability is limitless, each Ditto is no stronger or faster than their size suggests, necessitating distractions and trickery as opposed to outright fighting. Furthermore, the shared weakness of every single Ditto somewhat negates the usefulness of making large numbers of clones.

Ditto first appears in "Divided We Stand" as an accidental transformation.