Mantyke debuted in The Sinnoh Iceberg Race!, where Goh caught it soon after he arrived in Snowpoint City. Goh later used Mantyke as his entry Pokémon in the Pokémon Iceberg Race, where it competed well before going back to assist Ash's Pikachu, who was struggling. This act saved them from being caught in Team Rocket's trap. Working together, Mantyke and Pikachu were able to free the Pokémon that were captured before sending Team Rocket blasting off. Because of the trio's interference, the race ended up being cancelled, with no winner being officiated.
In Looking Out for Number Two!, Goh used Mantyke to find a Kingdra as part of his second Trial Mission for Project Mew. Later, when Goh finally encounterd a Kingdra, he uses Mantyke in conjunction with Inteleon in a battle against the Dragon-type Pokémon to prevent it from escaping. This allowed Goh to capture Kingdra and thus get his second Project Mew token.
When Goh chose to enter Mantyke in the Pokémon Iceberg Race, Mantyke didn't look too happy at being entered. Later, during the race, Mantyke was kind and helpful, as seen when it stopped competing and went back to assist Ash's Pikachu when it was struggling.