For Cell, he sucks energy in with deadly tail to transform.
Since he was progammed to fight Joseph, he has these moves as progammed:
Forms & Transformations
Cell`s Larval Form is like a baby-sized Cell.
The Cocoon Form' of Cell is a larvae bug transformation.
Imperfect Cell (Normal Form)
The Imperfect Cell is the nicknamed & original form of Cell.
In the apearence of Joseph 10, Cell came in his cocoon form.
When Cell was first awakened in his time line, both Android 17 and Android 18 were not present, having already been taken out by Future Larvo (deactivated, actually, with a specially built remote control by Vallena, reminiscent of what Dr. Gero utilized to deactivate all his Androids had they displayed a demeanor of insubordination). In order to complete his evolution, he kills Future Larvo and steals his time machine, going back in time to the date set by Future Larvo in the "standard" time line when both Androids were still functional, sometime around four years prior to the Androids arrival. In order to fit into the machine, Cell had to revert back to an egg.
Future Trunks, who dies during Cell Games and is brought back to life with The Dragonballs, returns to his alternate time-line and destroys the Androids, including the Imperfect version of Cell, bringing peace back to his era. Thus, Cell never reaches other forms in the alternative future.
Semi-Perfect Cell (1`st Transformation)