Ratty first appeared as a Rattata in Drat That Dratini! as one of the many Pokémon living in Viridian Forest. When Red met Yellow, he lent her his Pikachu, Pika, to capture her first Pokémon, which happened to be Rattata. With Red's guidance, Rattata was captured as Yellow's Pokémon.
In Cloystered, Ratty helped Yellow in her escape from Lorelei and her Ice-type Pokémon. When Yellow and Bill were trapped by a chunk of ice Ratty slips underneath it and uses Hyper Fang to drop it into the river, allowing them to escape.
In Paras Sight, Ratty battled alongside Dody against Super Nerd Miles in an attempt to rescue Pika. Completely pinned by Miles's attack, Yellow decides to give herself up to Marowak's Bonemerang, recalling Ratty and Dody before taking a direct hit to the chest. Although injured, Yellow attaches Ratty and Dody's Poké Balls to the bone, which come swinging back at him. Ratty and Dody then get released and help Pika to escape. When Miles pursue them the three release a combo attack, with Ratty breaking apart a nearby building with his teeth, Dody kicking them in the air, and Pika electrifying them and sending it at Miles, defeating him.
In Can't Catch Caterpie!, Ratty battled a wild Caterpie that Yellow wished to catch. The two spent all day trying but could not find a way to do it without hurting him. Blue eventually steps in and helps the two capture Caterpie. After the battle, Ratty evolves into a Raticate, much to Yellow’s shock and initial dismay. By the next morning, she had recovered from the trauma and declared that regardless of his appearance, Ratty is still the same Ratty, and it would not bother her anymore.
Shortly after evolving, Ratty gnawed the sinking S.S. Anne in two to help Yellow defeat Ken, Al, and Harry.
In Eradicate Raticate!, Ratty is sent out alongside his teammates to battle against Lance and his Dragonite. Ratty attacks with a Super Fang, but Dragonite simply shrugs it off and throws Ratty away. He is later used in a team attack to try and stop Lance from shooting bubbles. Yellow had Kitty cover the volcano crater in String Shot to form a net that is doused by her Omny's water, linked to Ratty's sensitive whiskers. Upon Lance triggering the net, Ratty signals to Pika to send electricity down the net, forcing Lance's bubble into view. Yellow then orders Dody to break the bubble with Drill Peck, but the attack proves too weak.
In The Might of... Metapod?!, Ratty participated along the rest of Yellow's team to battle Lance and assisted in defeating his team.
In The Last Battle VII, Ratty was seen defending the Day Care Center with the rest of her Pokémon from the half-masked Team Rocket Grunts.
In Down-for-the-Count Deoxys, Ratty helped open a way onto the Team Rocket airship.