Matt Bird writes all sorts of nonsense, but he dedicates a large chunk of his time to writing game walkthroughs.
One of many members of Chrono Cross' expansive cast, Pierre holds the distinction of being, unless you give him the right gear, perhaps the worst party member you can recruit. Not only is he incredibly weak, bringing him onboard forces you to miss out on two superior party members during your current playthrough - one of whom is one of the best party members you can get.
Still, if you're determined to make Pierre a member of your merry band, this guide will help you track him down and put him in your party. Be warned, however: He won't achieve his full potential (such as it is) for quite a while, and in the meantime, he'll largely be a burden in combat.
Before you can recruit Pierre you need to get to the early section of the game where you're about to invade Viper Manor. This means going to Lizard Rock - in both worlds - then heading to Termina in Another World, via Cape Howl and Fossil Valley. It's early in the game so you won't need to wait long.
At this point, whether you accept Kid into your party or not, you'll need to head to Viper Manor next. It's the game's first major dungeon, and there are three characters who can get you inside. Pierre just happens to be one of them. You'll find Pierre in Termina, not far from where you speak to Kid.
Go east from the entrance of Termina, then north when you find an intersection with a fortune teller. This will bring you to Termina's Smithy. Go through the front door, then back through the smithy itself and into a back room. Pierre is back here, clearly ready to join the Four Devas of Viper Manor - though he bemoans the loss of his 'symbol of heroism'.
Go through the door in this same room that leads back outside. You'll be in a small yard between the Smithy and a log cabin. A boy will be running laps around the yard. Speak to him and he'll give you the Hero's Medal, Pierre's missing trinket. Take it inside and show it to Pierre as a key item. He'll happily reclaim the Hero's Medal, and if you talk to Pierre again he'll insist on joining you when you head to Viper Manor.
Be warned! This is your only chance to get Pierre during this playthrough. If you accidentally accept Guile instead, or agree to help Miki find Nikki, you'll eliminate Pierre as a party member. Stay far away from Guile (in the bar) and Nikki (in the Shadow Forest, though you need to head to Termina's docks first) to ensure you get Pierre. Similarly, you can't get either Guile or Nikki if you recruit Pierre.
Read More From Levelskip
(As a side note, it's possible for Pierre to be a part of your party at the very beginning of the game, as well, alongside Serge and Kid. You can't control whether he'll appear, however, so just cross your fingers.)
Maximizing Pierre's Potential
On his own Pierre is... not great. His stats are all below average, and the majority of his attacks will do next to nothing. You won't want to use him for anything besides getting into Viper Manor until you've retrieved two other pieces of equipment.
The Hero's Shield is the earlier, easier piece of equipment to get for Pierre. You'll find it during your trip through Viper Manor, in a treasure room. Get caught in the entrance of the manor by getting the number combination in the entry hall wrong. This will drop you into a cage. You'll be freed one way or another (depending on how things are going with Kid) shortly thereafter.
Once you're free and disguised, go through the rounded cage doorway on your right. There's a treasure room here, just before you meet a robot that's blocking the hallway. Inside there are three treasures at the far end. Grab the Hero's Shield that's on display nearest the painting on the wall. You can also steal the Copper Sword and Copper Mail that are on display to give Pierre a bit of a boost, assuming you're grabbing this stuff during the Viper Manor heist.
The second item you'll need, the Prop Sword, isn't found until much later in Chrono Cross, and you'll need to have gained access to the Dead Sea. Enter the Tower of Geddon and proceed through it until you reach a large, rubble-strewn area with a patch of greenery in the north. The Prop Sword is on the left side of the grassy area, sitting by itself.
Take the Prop Sword back to Termina once Pierre is available as a party member again, but not in your active party. He'll be in his rented apartment in the rear of the Smithy, right where you recruited him in the first place. Giving him the Prop Sword will turn it into the Hero's Blade, and Pierre will learn the SlapofCyrus Tech. (He'll also gain some enthusiasm for training.)
Once Pierre has the Hero's Medal, the Hero's Shield, and the Hero's Blade equipped he'll become quite a bit more powerful... though that makes him about average with everyone else, rather than sitting at the rear of the ranks. Ah well. At least he's usable.