Raticate first appeared under the ownership of a Gentleman aboard the St. Anne, easily defeating a Trainer's Starmie in a battle. Seeing how strong Raticate was, Ash challenged the Gentleman to a battle, using his Butterfree against Raticate. Butterfree easily endured and dodged all of Raticate's attacks, and then paralyzed it with Stun Spore. Before Ash could order the finishing move, however, the Gentleman called off the battle, saying that it was a draw, although Ash was close to winning.
Afterwards, the Gentleman came to tell Ash that he was so impressed with Butterfree that he wanted him to trade it for his Raticate. Ash, although being impressed of Raticate's strength too, was uncertain of what to do, and asked Brock for advice. Brock told Ash to agree to trade, although given the fact that he was infatuated by the Gentleman's beautiful woman companion at the moment, he likely wasn't even fully paying attention to what they were talking about. Thus the trade was made, making Raticate Ash's newest Pokémon. Later Ash told Misty about how he was still uncertain if the Gentleman would take care of Butterfree the way he did, and was thinking if he even made the right decision by trading it away.
Ash only used Raticate once, mistakenly calling it out when he wanted to use his Butterfree to help fighting against the group of Team Rocket Grunts on board, having momentarily forgotten the trade had happened. Finally fully understanding how much he missed his Butterfree and how worried about its well-being he was, Ash came to realize that the trade had been a bad idea and he would rather have his first caught Pokémon back. The Gentleman agreed to trade Butterfree back, and the original trade was reversed while the St. Anne was sinking. Due to this delay, Ash and his friends got trapped inside as the ship sank into the depths. Neither Raticate nor its Trainer have been seen since.
Personality and characteristics
Since Ash only owned it for less than an entire episode, little can be said about Raticate itself. There is not enough known about it to even distinguish it from other Raticate, apart from the fact that it can use Jump Kick, a move that cannot be learned by other Raticate, and that it is, in general, a strong Pokémon.