Cell

Cell was the ultimate creation of Dr. Gero, who was designed to possess the abilities of the greatest fighters that visited or inhabited Earth; the result was a "perfect warrior"' possessing numerous favourable genetic traits and special abilities. He was one of the few Red Ribbon Androids that was completed by Dr. Gero's Super Computer

Appearance
In his imperfect form, unlike his larval form, Cell walks hunched over, his facial features have not yet fully developed, and he still retains an orifice like mouth (which obscures his sharp teeth), as revealed in "Silent Warrior", rather then traditional human like features seen in later forms.

Personality
Cell has an original personality, with various other characters' personality traits added; in Gero's computer redesigned the weak parts of the original personality, adding in the personalities of various different characters to make him the perfect weapon. Throughout the Android Ark, Cell's personality changes drastically with each transformation

Cell Saga
The version of Cell that plays a large role in Dragon Ball Z hails from an alternate future timeline where he has already evolved to his imperfect form. Unfortunately for him, neither Future Android 17 nor Future Android 18 are present, having already been taken out by his version of Future Trunks.