Grass Hysteria! (Japanese: 禁断の森の王者！フシギバナ！！ King of the Forbidden Forest! Bulbasaur!) is the 33rd episode of Pokémon: Advanced Challenge.
The heroes get lost in a forest. Just then, May gets taken away by a Skarmory. As Ash, Brock and Max try to get May out of the forbidden area, May befriends a Bulbasaur, but the Grass-type Pokémon start attacking her.
The heroes are lost in a forest, as Max's PokéNav cannot get a signal and Brock's compass shows different directions. May is quite frightened and out of sudden, a Skarmory begins to chase them. May's Skitty goes out and May protects it, but in so doing, Skarmory grabs her and sends her away. Ash, Brock and Max go after Skarmory, but encounter two men blocking the path. They explain that nobody is supposed to cross to the other side of the gate. Ash, Max and Brock explain May's been carried there by a Skarmory, so the men go to speak with Old Man Ogee, so the boys follow them as well. May is carried on a peak, where the Skarmory leaves her and flies off. She calls Skitty back to a Poké Ball and sees a Bulbasaur. Bulbasaur gets a flower, but begins to fall down, so May grabs it in time. Despite its friendliness, Bulbasaur takes some steps back. May introduces herself to Bulbasaur, who tickles her using a vine. However, a Sunflora, Weepinbell and a Vileplume arrive to defend it.
The old man is told about the problem, but cannot help Ash, Brock and Max, as the Grass Pokémon will be angry, since the area is forbidden to humans. Nevertheless, they will go to see how to deal with the situation. Team Rocket spies on them and they plan to steal the Grass Pokémon and give them to the boss. Sunflora uses Razor Leaf, Vileplume Stun Spore and Weepinbell Vine Whip on May, defending the Bulbasaur. Bulbasaur attempts to calm them down, but more Grass Pokémon arrive to attack May. To protect herself, she sends Torchic to use Ember. Torchic negates the attacks and runs off with May. Bulbasaur tries to go as well, but is stopped by a Sunflora. As the men discuss, Ash, Brock and Max leave to go get May. The men notice Poochyena barking and notice the heroes have left already. Brock, Max and Ash tackle the gate, but they have to climb the vines to get across. Some of the vines break, causing Brock and Max to fall down. They ask of Ash and Pikachu to go get May back. May is hiding, but is forced to go away, due to Stun Spore being emitted. Suddenly, she is surrounded by the Grass Pokémon. However, Ash arrives to the scene.
Pikachu uses Thunderbolt, clearing a path for them to escape. As they are running, Ash explains to May this is a land, forbidden to humans, even if May didn't come here by choice. Pikachu uses Thunderbolt for Ash and May to pass. While their path is blocked, Torchic points at another path. However, they stand on an edge of a cliff. May tries to convince the Pokémon she won't hurt them, but the Pokémon refuse to listen. The Grass Pokémon attack, but a Venusaur yells out, canceling their attacks and approaches them. Venusaur checks Ash, May and Torchic, for Bulbasaur May rescued earlier has warned Venusaur that they are not for any fighting. Meowth translates this and as James remarks how the Venusaur is huge, Jessie plans on stealing them, thinking Venusaur is quite powerful. Ash and May are taken to a waterfall. Bulbasaur gives May the flower, reminding Ash of his own back in Pallet Town. Bulbasaur grabs May with a vine, going off, so Ash goes with her, while Venusaur observes.
Ash and May see the forest they have been lost in before. May sees a town and explains to Bulbasaur there is a large world out there. May lifts Bulbasaur up and tells she and her friends have been through towns like that one for a lot of time, which makes Bulbasaur happy. Old Man Obee explains to Max and Brock the Grass Pokémon were hunted by men, so they became enraged. To prevent any damage, some people built the gate for protection. The land emits a magnetic field, preventing some machines to work. As May observes the view, Ash reminds her Brock and Max are worried about them and they shouldn't even be here. Suddenly, Team Rocket begins to steal the Grass Pokémon. Pikachu uses Thunderbolt, but the attack is deflected due to the mirror Team Rocket has added to the machine.
As he men, Brock and Max are searching, Max carries a rope, so everyone can return back to the gate later on. They hear the Bulbasaur being taken by Team Rocket. Venusaur attacks Team Rocket machine, which drops Bulbasaur down, but is rescued by May. Team Rocket goes to take it, but Venusaur uses Vine Whip and goes to take the Grass Pokémon. Meowth accelerates, making Venusaur harder to take the Pokémon back. However, Meowth switches the direction to backwards, so Venusaur is knocked out. Team Rocket takes Bulbasaur, though May grabs on the robotic arm, which places them in the storage unit. May sees they have to do something, while Ash and Pikachu help Venusaur get back on its feet. Just as the machine is about to grab Venusaur, the Pokémon tackle the robot's bag. Per Ash's advice, May has Bulbasaur uses Razor Leaf, freeing all the Pokémon from the robot. But, just as the robot is about to recapture the Pokémon, Obee's Poochyena use Shadow Ball, blowing the hand to pieces.
Pikachu uses Thunder, but the attack is deflected by the mirror. However, Venusaur uses Solar Beam, blasting Team Rocket away, as the robot wasn't able to counter it. Later on, everyone apologizes to the Grass Pokémon for disturbance. Just as the gate is to be closed, May says goodbye to Bulbasaur. However, after some thinking, Bulbasaur goes to May, joining her as its trainer, while the grass-type Pokémon approve of Bulbasaur's decision. May is glad she and Bulbasaur found a new friend today, while the heroes are glad Bulbasaur is on their team.
- Featured Pokémon: Manectric, Electrike, Mantine, Electrode.
- In the beginning of the episode, a classic Pokémon identification can be seen. In this case, it is a Charmander.
- The title is based on the phrase 'Mass hysteria'.
- This episode is featured on the Volume 1: Grass copy of Pokémon Elements.