Pokemon the Series: Ruby & Sapphire Season 601 Episode 9 Taming of the Shroomish

When Ash and friends stop in Rinshin Town for food and supplies, May drags Brock off to see a haunted mansion. Meanwhile, Max spots a Shroomish in an alleyway, which is odd because Shroomish normally live in forests. It turns out that the town used to be a forest where many Shroomish made their homes, and they've since been edged out by urban development. But they've been gathering in the mansion, which explains the odd things people have been seeing there. The mansion is now scheduled to be demolished, leaving the Shroomish homeless once more. But after these helpful Pokemon stop a Team Rocket attack with a combined Stun Spore, the mansion's owner decides to tear down the building as planned, and then convert the entire property into a new forest home for the Shroomish!