Callima was a Paras who lived in Mt. Moon along with the other Paras, including her friend Deidre. While wandering once, she found herself fighting Radic's Pokémon and she lost, becoming captured. Not minding particularly, as she had been somewhat bored, she found that Radic appealed to her. The quiet boy seemed to really need her, and appreciated her input and effort when in battle and out of it. She became very attached to him and vowed that she would protect him with her life.

Callima got along well with the other Pokémon, due to her extraordinary patience and her kindness. She was one of the few to speak honestly with Kitsune, to convince her to stay alive and come with them. She was able to calm almost any of them down, even the hysterical Takachan, then Taka at that point.

While walking through another cave, Callima was shocked to meet up with Deidre again, which was a pleasant reunion. Deidre was heading to a grand meeting to be evolved and invited Callima to come. Thinking that if she evolved, she'd be able to help Radic even more, she went to the ceremony, willing to brave the pain. However, it wasn't until she was there, and Radic and the others had followed her, did she find there was a slight complication. She had been trained and had the scent of humans about her, and this was unacceptable to the lead Parasect who evolved the others, including Deidre. When Radic protested how they were treating her, the congregration turned on him instead. Callima couldn't stop them by herself, and things were looking grim until Deidre, now a Parasect, stepped forward and attacked the Elder Parasect, giving Callima and her trainer enough time to make it to safety.

Easily outnumbered, Deidre quickly fell. As she died, her mushroom gave off the same powder that had evolved her, and it touched Callima. With pain, Callima evolved, her heart filled with anger and sadness at her friend's needless death. Hurt and angry and desperate for vengeance, Callima released the ultimate and forbidden powder attack of the Parasect...Deep Sleep Powder. She regretted it almost immediately, but the deed was done. She and her companions ran before the dust could touch them, but the rest of the Paras present were not so lucky.

The experience made Callima more introspective, yet didn't change her completely. She still extended kindness and her claw to almost everyone, never wishing to foster the spread of hatred again. Callima is tolerant and patient to a fault, willing to step in when conflict arises, and obedient to Radic in battle, no matter the cost. She will fight bravely for Radic or the others and trusts in Radic's judgement and decisions, even when it puts her or her teammates in an awkward position. She feels very close to Radic, as he often confides in her.

Other Paras and Parasect make her somewhat nervous though, as she suspects that she's been permanently ostracized from the Paras/ect community for what she'd done.

Callima has been in fics where Radic has his Pokémon.

Callima has been mentioned in several fics.