706.2. When copying an object, the copy acquires the copiable values of the original objects characteristics and, for an object on the stack, choices made when casting or activating it (mode, targets, the value of X, whether it was kicked, how it will affect multiple targets, and so on). The copiable values are the values derived from the text printed on the object (that text being name, mana cost, card type, subtype, supertype, expansion symbol, rules text, power, toughness, and/or loyalty), as modified by other copy effects, by as . . . enters the battlefield and as . . . is turned face up abilities that set characteristics, and by abilities that caused the object to be face down. Other effects (including type-changing and text-changing effects), status, and counters are not copied.

If the chosen creature has Variable Colorless in its mana cost, that X is considered to be 0. The value of X in Altered Ego’s last ability will be whatever value was chosen for X while casting Altered Ego.