Chuchu was caught about three years after Yellow's first appearance in the Red, Green & Blue chapter. In Tyranitar War, Yellow mentions that she found Chuchu injured in Viridian Forest and took her in. After introducing her to her uncle Wilton, he notes that Chuchu had grown quite attached to her and expounded on his real objective, which was to ask Yellow to go to the Johto region with him to investigate about Lugia. Because the sheer magnitude of a monster that they are dealing with does not leave him with many options alone, he needed someone to go with him, and Yellow came up with the idea to ask Red. After Yellow found him training near Viridian Forest, Chuchu seemed to take a liking to Pika soon after they met. However, with Red's wrists and ankles still weak from the damage that Lorelei's ice cuffs left on them, he needed to recover at the hot springs of Mt. Silver, and left Pika behind. Alongside Pika and Yellow, Chuchu flew to Johto on Kitty with Wilton's Butterfree.
In Do-Si-Do with Dodrio, they encountered Crystal after the latter mistook Pika for a wild Pokémon. Soon, however, the two Trainers got involved in Lugia's rampage and lost consciousness in the shipwreck.
Following the incident, Chuchu and Pika produced an Egg in Playful Porygon2 when Pika spent time with her in the Johto Day-Care Center. When some Team Rocket members attacked the Day-Care Center, Chuchu, in a desperate attempt to protect her egg, flew, with the help of balloons, carrying Pika and their Egg. When the Masked Man took the three hostage near Ilex Forest, Gold embraced their Egg and took a number of blows to guard it, hatching the Pichu that the Egg contained. With Pichu's assistance, the boy eventually succeeded in defeating the villain, and Chuchu's offspring was left in his care.
In Secrets from Sneasel, Yellow and Chuchu enter the Viridian Gym to see if Blue and Red have returned. They find the Gym empty when suddenly a hologram of Blue appears from behind Yellow. The hologram is revealed to be a pre-recorded message designed to battle challengers even when Blue isn't in town. Chuchu tells Yellow that she wants to fight, so Yellow decides to take the challenge. Blue's Pidgeot starts off the battle with Feather Dance and follows up with Wing Attack. Next, Alakazam is sent out and uses Role Play to copy Chuchu's Ability, Static. Alakazam uses the Ability to paralyze Chuchu, defeating her.
Through a chain of events, she later found herself in Red's hands after Yellow spent the last of her energy informing him of Deoxys's message, and assisted in defeating Carr's ten Forretress.
Two months later, she and Pika, who were thankfully able to escape the beam that left their Trainers petrified, traveled with Gold and Crystal to the Hoenn region to help save Jirachi. Soon, Gold also revealed that the two and his own Pichu, Pibu, had learned Volt Tackle to help out, and after the remaining five of the Pokédex Holders succeeded in freeing their comrades, the three dealt the finishing blow to Guile Hideout's giant Kyogre monster.
Personality and characteristics
Chuchu, Pika, and Pibu
Chuchu is a kind and caring Pokémon, much like her Trainer. Chuchu cares greatly for Yellow and is often the only one of her teammates outside of her Poké Ball. Despite Yellow not being much of a battler, Chuchu has shown that she is able to fight and occasionally insists on participating in battles. Upon meeting Pika she instantly sparked a connection with him and has since become his mate. Chuchu also cares greatly for her son, Pibu.