Percier is an original character exclusive to Metal Slug Attack.
A small girl with green hair, she considers herself to be the "eternal assistant" of the Professor. She didn't share his interest in Martian technology, however, and he abandoned her while leaving the Rebel Army.
She looks and acts like a Martian, as she notes that the Professor seems to pay more attention to her when she has her costume on. She dislikes the Martians out of jealousy because they "stole" her "beloved". The Professor considers her to be somewhat boring and treats her rather poorly, as shown with the majority of his humanoid creations showing a lack of respect for her.
First appearing in the Extra Ops "Mad Scientists", she helps the Professor break into Navy's lab. When the Professor is defeated, she arrives just in time with Marty to save the Professor and leave.
She makes a small appearance in the third Try Line, where she tells Gemini Black & White to be careful on their raid on a Rebel supply line. When White comes back injured from a K-03 Coupled Armored Vehicle's attack, she quickly applies first aid to them and Black thanks her by handing her some United Coins. She then goes to check on the Professor.
When Abigail makes a surprise attack on the Martian base, Percier takes the Gemini Twins to deal with the threat, encountering a locked door. Black forces the door aside and Percier is shocked to see the Professor dead in front of her.
During Christmas, Percier and Marty head to Earth and wish to see the Professor again. When they see Teleko and Chloe fighting, the two try to intervene so that the Invader does not take all the trees, but are too late. Percier cries as her wish will never be fulfilled, but Marty reinvigorates her by stating that researchers never give up, something which they heard from the Professor himself.
Percier appears in the story "For You", where she appears being chased by rebel soldiers. Upon being saved by the Professor and his allies, she tries to act like a Martian, but the Professor's Martian comrades do not understand what she is saying. The Professor easily recognizes her, and having no point in leaving her this time, allows her to tag along. During this story, her relationship with the Professor is shown, and she also becomes "friends" with Marty.
In the first Halloween chapter, Percier appears having been assigned by Aswang to bring Vatn to her. Vatn, who had been hired by Whip, manages to bring Caroline over, who then defeats Percier in battle. Vatn learns of Percier's "boyfriend" (the Professor) and reassures her that they are lucky to have her, which gets her excited and she joins the group.
When Clone Abby and Betty return from their mission on Earth, Clone Abby starts showing more respect to the Martians. Percier gets trampled by a Mars Mecha and yells at Clone Abby to watch out for her too; the clone coldly states that it does not need to take care of her as per the Professor's orders. Percier becomes heartbroken and begins to cry, prompting Marty to reassure her.
- Along with Heidern, she is one of the few purchasable units that makes a cameo before their debut.
- Upon victory, she typically plays upon a Neo Geo Pocket with a wireless unit attached. Her large hood hides an ahoge.
- If the Professor is in the same deck as her, this changes to where she thinks about the Professor.