A Six-Pack Attack! (Japanese: オーキド博士とオダマキ博士！秘密基地の戦い！！ Prof. Oak & Prof. Birch! Secret Base Battle!!) is the 31st episode of Pokémon: Advanced Challenge.
The heroes decide to stop at Professor Birch's lab. Hearing Professor Oak will come to the lab as well, Ash and Brock decide to accompany Birch to escort Oak to the lab. However, Professor Oak arrives by a cart and greets May and Max, the latter being a big fan of his. Once Team Rocket steals the Birch and Oak's Pokémon, May, Max and Professor Oak decide to go after them and rescue the Pokémon on their own.
Ash gazes his five badges, proud he only has three more to obtain for the Kalos League. He asks Brock where is the next Gym and is told it lies in Fortree City. However, Max and May remind him they need to see Professor Birch first. They arrive in to Birch's lab, but a car flies from a top of the cliff, goes past them and nearly crashing itself. The driver is Prof. Birch, who greets the heroes. He admits he caught up in his field work and forgot he had to meet up with Professor Oak at the docks, wanting to meet him for the first time. Ash and Brock go with Birch while May and Max will stay in the lab for a while. Max is exceptionally happy he will meet Professor Oak in person. While driving, Birch sees a Skarmory on a peak and greets it from afar. However, a cart is passing by, making Professor Birch nearly crash into it, as he passes by it. However, in the cart, a man is taking a break.
At the lab, Max and May see the new Starter Pokémon with Birch's assistant. May remembers the day she started her journey, by being startled by a Duskull and even got attacked by Professor Birch's Mudkip. May claims that was an exciting day, but Max thinks May stayed the same since that day. Max annoys May, who chases him away. Max replies he was just joking around and bumps into a man, who is Professor Oak. Max is amazed to meet him and starts examining him, then he shows photos of Professor Oak from the magazine he got. Thus, Oak writes an autograph for Max. Oak wonders where Ash and Brock are and Joshua, Birch's assistant, reports they rode in Birch's car to pick Professor Birch at the port. Oak admits he thought Professor Birch forgot about him and decided to go to the lab. Max wonders which Starter Pokémon are in Kanto, so Oak sends Bulbasaur, Squirtle and Charmander. Max is psyched to see these Pokémon
Team Rocket oversees the event, so Meowth thinks if the boss got all six Starter Pokémon, he'll be happy to have them as friends. Max is glad to see Bulbasaur up close, admitting he learned a lot from Professor Oak's lectures. Max touches Bulbasaur's bulb, but it gets angry and tackles him. He goes to see the other two Pokémon and starts touching, but Squirtle uses Water Gun and Charmander Ember, since they are quite annoyed by Max. Oak is amused and admits he learned their attacks in a similar way. Bulbasaur wants to meet May, so she shakes its vine. Suddenly, the group sees a giant Skiploom approaching them, which is a robot, made by Team Rocket. Team Rocket steals all the Starter Pokémon, so May, Max and Oak run off to save the Pokémon, while Joshua stays to guard the laboratory. Meanwhile, Ash, Brock and Birch wait for Oak and since they can't find him, Birch calls Joshua. He hears that Team Rocket has gone with the Starter Pokémon, so they need to after them as well and asks of Joshua to find something that belongs to Oak, May or Max.
Elsewhere, Oak knows Team Rocket did not just wander off so easily in a giant Skiploom and notices something behind the waterfall. It is a cave, which is lit by electric bulbs. Joshua shows Birch Max's backpack, who takes it and drives away. Oak, Max and May sneak in, but accidentally Oak triggers the laser, closing the main door and warning Team Rocket. Oak, May and Max see the Pokémon and go after them, but fall into a hole. May goes to bring her Pokémon, but the Poké Balls are sucked into the vacuum cleaner and Team Rocket wanders off with the Pokémon, while the hole gets closed by iron bars. Birch drives away, claiming his friend lives in here, though Ash, Pikachu and Brock are terrified, since they are on rocks and not on an actual road. Max thinks he might be small enough to squeeze through the bars, but Oak asks if he can borrow Max's photos. Team Rocket celebrates, but James thinks they should see the captives. Meowth shows on camera they have nothing to worry about, but in truth, a picture of Professor Oak is displayed, fooling them.
Max squeezes through the bars and has to free the Pokémon. Max needs to order the Pokémon to use a Fire, then a Water Attack and Tackle to set them free. Torchic and Charmander use Ember, followed by Squirtle and Mudkip who use Water Gun and, lastly, Treecko uses Pound and Bulbasaur Tackle to destroy the bars. The Pokémon are freed and start hugging Max, tickling him. Elsewhere, Ash and Brock wait for the friend to come, so Birch whistles a tune, causing a Poochyena to appear. Poochyena smells Max's backpack and runs towards Max, so Birch, Brock and Ash follow it. The Pokémon free Oak and May, but they also need to get May's Poké Balls back. May sees them partying, so Oak thinks of a tactic involving Zubat and bulbasaur. Team Rocket are affected by Zubat's Supersonic to distract them, while Bulbasaur uses Vine Whip to get May's Poké Balls. They all go towards the entrance, but find it closed. An alarm is heard, warning Team Rocket, who sees them at the entrance. Jessie notices a photo of Professor Oak, which falls down. Meowth presses a button to seal them, lowering down the bars. Some Dugtrio appear, so May, Max and Professor Oak go through Dugtrio's tunnel.
At the end of it, there is a lake with a sleeping Gyarados. Team Rocket go furious when they see Max, May, Oak and the Pokémon escaped through the hole. Meowth goes through the tunnel and is startled by the sleeping Gyarados. As Jessie and James yell and argue, Gyarados wakes up and attacks them using Hydro Pump. As Ash, Brock and Birch follow the Poochyena, Birch spots that Zubat live outside and Poliwrath in the lake and points out normally Poliwrath live near the waterfall and Zubat inside the caves. Meanwhile, May, Max and Oak go towards the exit, but find it sealed. Max yells through a small hole and Poochyena goes after the source. Ash, Brock and Birch hear Max's voice. Oak studies the door and realizes they need to attack using a combination to destroy the door. Oak asks of Ash to use Water attack and then Thunderbolt.
Brock sends Lombre and Mudkip, who use Water Gun on the door, with Pikachu following up with Thunderbolt. Afterwards, May's Skitty, Squirtle, Mudkip and Bulbasaur tackle and Treecko pounds the door, knocking it down and freeing the group. However, Team Rocket turn the Skiploom machine on and try to capture the Pokémon. Pikachu uses Thunderbolt and Lombre and Mudkip attack with Water Gun, but with little difference. To destroy it, they need to use a combination of attacks. Charmander and Torchic use Ember, Mudkip and Lombre use Water Gun, and Skitty uses Blizzard, which cracks the machine. Pikachu uses Thunder, destroying the machine and blasting Team Rocket off. The next day, the heroes board on the ship and bid farewell to Professor Oak, Professor Birch and Joshua.
- Featured Pokémon: Slowking, Jolteon, Nidoqueen, Makuhita.
- At the beginning of the episode, a classic Pokémon identification can be seen. In this case, it is a Clefairy.
- May befriending Professor Oak's Bulbasaur and Squirtle appears to foreshadow the capture of her own members of both species later on in the series (one of which would actually be intended to be a starter).
- When Team Rocket is seen blasting off, Jessie, James, and Meowth form the letter "R".