Ben 10: Alien Force

You can't because the How to unlock Goop cheat is a fake, other than that there is no other way to unlock other aliens.

All Ben 10 games are only with 5 aleins (That sucks)
but with all 10 aleins..the Game can get too complicated....like just say theres a wall,and you forgot which alen can get through...so the Makers of B10 decided to get only 5 aliens in the Games....so no Cheats to get all 10..because the other 5 where never made..

Sadly, the game only has 5 aliens.. Anyone telling you how to get other aliens are trying to lie to you.

I am still wondering what is the last question mark on "Hero viewer" there for.

The last question mark on hero viewer is grandpa max

Just go to ds version

You can't unlock anymore aliens than those 5.

You can use Chromastone, Echo Echo, and Goop in the DS version with the replacement of Big Chill, Spidermonkey, and Humongasaur in the PSP.