The Pigmasks are creatures that are controlled by Porky. Their main goal is to pull out the Seven Needles and awaken the Dark Dragon. Of course, Porky and the Ultimate Chimera would be the only two things to survive this, as Porky is in the Absolutely Safe Capsule, and the Ultimate Chimera is invincible.
There are different ranks of the Pigmasks. These go from Pink being the lowest to White being the highest. This also works with stats for the enemies. The lower ranks will carry a Beam Gun, while the higher ranks will either use PSI or Bash into you for massive damage.
The Pigmasks are first mentioned in the Prologue when Hinawa is sending a letter to Flint. After the pigeon carries it away, a hovering object flies overhead, which is a Pigmask Trooper Ship. They are first seen at the beginning of Chapter 1, when two Pigmasks are throwing a Pork Bomb into the Sunshine Forest, which results in the events that cause the entire game to start. They appear in every chapter except chapter 6, as that is an incredibly short chapter that only Lucas, Hinawa, and Boney are even mentioned in.
Most of them are weak to PK Freeze, so it's always a smart thing to start out with that. Of course, none of their creations are weak to PK Freeze, so you'll usually use Duster for things like that. They're incredibly easy enemies, and they don't take long to defeat. PK Freeze Ω will do over 500 damage to even the Pigmask Commander, or the White Pigmask. The Fierce Pork Trooper is one of the only Pigmasks that is not vulnerable to Ice, but vulnerable to DCMC items, such as the DCMC Pamphlet and DCMC Boxers. Any DCMC items will work. You also fight him twice, once in pink, but still very strong, and once in blue, but even stronger. They're basically the same creatures, just with a small difference in stats... and I guess color.
If your going to use the boxers on him, be sure your ready for some painful mental images.