How do you get all 10 aliens on ben 10 protecter of earth on psp?

Answer 1

you can only get 5 alien; Heatblast, Fourarms, Cannonbolt, XLR8 and Wildvine.

In the final cutscene only, before the null void bonus level, you unlock all the aliens that were not playable.

Answer 2

wildvine fourarms heatblast wildvine but, you only get the 5 in the game, no more, no less