Pex and Chips are villains from the novel Artemis Fowl: The Eternity Code, by Eoin Colfer. They are henchmen who work for Jon Spiro and Arno Blunt. They are known to be extraordinarily stupid, and act as comic relief throughout the story.
Both Pex and Chips were interviewed for a job to work for Jon Spiro. They were told to smash a walnut. Pex shouted at the walnut for a few minutes before crushing it in his palms. Chips grabbed the interviewer by his ponytail and smashed the walnut with his forehead. Both were hired on the spot.
They worked as bodyguards for Spiro, under the command of Arno Blunt. They couldn't do any job outside of Chicago, as neither of them could read a map. Chips used his earnings to buy Barney DVDs. Pex and Chips would argue about whether Barney was better than other fictional characters like Captain Hook.
The Eternity Code
After Mulch brought Artemis to Spiro, they were told to kill Mulch. Mulch easily insulted their intelligence, and tricked them into burying him alive. They did this without question, not knowing that Mulch could tunnel through the earth instantly.
Later, they were sent to a mysterious van where Juliet Butler was. Juliet pretended to be lost, and then they got into a discussion about frying sushi. Juliet knocked them out with her jade ponytail. Holly mesmerized them not to recognize Artemis. Later, when Artemis went to break into Spiro's vault, both Pex and Chips couldn't see him.
Spiro took Pex and Chips with him to Phonetix to use the C Cube to steal trade secrets. Artemis was brought with them, though Pex and Chips couldn's see him. Artemis tricked Spiro and escaped. Pex and Chips claimed Artemis was never there, which caused Spiro to go crazy and shoot up the place. Pex and Chips thought it was fun and started shooting the place too.
It is not explicitly stated what happens to them, though it is implied that they were arrested along with Spiro.