In the past, Grandpa Forest met Lana and Mallow soon after they first met and became friends. When they first encountered Grandpa Forest, they were scared off. Grandpa Forest eventually reappeared when Lana and Mallow fell off a cliff and saved them. This led to Lana and Mallow becoming friends with Grandpa Forest.
Grandpa Forest flying
In Tasting the Bitter with the Sweet!, Lana informed her classmates about an encounter that her sisters had whilst in the forest when they got lost. This led Mallow and Lana to remember when Grandpa Forest saved them and they believed it was the same Pokémon. After school, Ash accompanied Lana and Mallow into the forest as they recalled their adventure. Rotom eventually concluded that Grandpa Forest was a Drampa based on the description. They soon encountered Grandpa Forest, who was happy to see them. Soon after, Team Rocket, who had been spying on Ash, Mallow, and Lana, showed up, dressed inPreschooler apparel in an attempt to woo Grandpa Forest. Grandpa Forest didn't believe their ruse and attempted to fly off, only to be captured in a net fired by Meowth. Infuriated, Grandpa Forest easily freed itself and attacked Team Rocket, who was promptly saved by Bewear. Lana thanked Grandpa Forest for saving her sisters and they spent some time together.
In Spying for the Big Guy!, Team Rocket attempted to capture Grandpa Forest to give to Matori after she arrived in Alola to take Bewear. After luring Grandpa Forest to them with Haban Berries, Team Rocket sent out Mimikyu to battle it, but as Mimikyu was only interested in battling Pikachu, it refused to fight. James then sent out Mareanie, and they were about to attack Grandpa Forest with Black Hole Eclipse when Bewear and Stufful showed up and brought them back to their hideout.