Go to Monkey Gong Level 7, shoot the construction blocks on the right side only and then quickly move to the left side and wait until the mother-glob filled up the screen nicely. After that, shoot the helmet-enemies until they drop the weapon you need to do the combo with and then perform it on the mass of small globs - here is a picture of the setup:


Zing! You earn the achievements and therefore add the internet-street-credibility straight to your account.