It is believed that Geurillas were probably wild in nature, but this is uncertain, because they are not native to the Mushroom World Smithy brought the creatures with him when he invaded, and used them as slaves and ground troops during his invasion. According to Mario and Luigi, similar creatures existed in the world they came from.
Since Smithy was defeated, not many Geurillas have been spotted. It remains to be seen whether or not they can survive in the Mushroom World's foreign environment.
Attack Pattern: Geurillas use a fairly even mix of regular attacks and Earth Toss. The Earth Toss move simply involves tearing up a large chunk of dirt and rock from the ground, and throwing it at opponents, but don't underestimate it, it is a very powerful attack.
Basic Fighting Strategies: According to the SMRPG Player's Guide, CKs are strong against fire, but I didn't find this to be the case. In fact, fire is more effective than anything else (except possibly for Ice, which I haven't tested yet.)
So, if you want to dispatch of these guys fast, use one of Mario's fire attacks. Otherwise, regular attacks should work pretty well, they just take a long time to wear him down, with his 355 HP.
Advanced Strategies: Save these guys for last during battle. They are dangerous because of their high offensive and defensive ratings, but they can't use any magic spells, so they can't really put you in danger as long as you keep healing your party.
As for blocking, they move toward the character they're going to attack, raise their arms, and then try to "crush" the character. It is a bit difficult, but if you press A just before the "crush", you should be able to block them.
