An Old Family Blend! (Japanese: 熱戦前夜！サトシのポケモン大集合！！Eve of Battle! Satoshi's Pokémon All Together!!) is the 182nd episode of Pokémon the Series: Diamond and Pearl, and the 648th episode of the Pokémon anime. It first aired in Japan on June 24, 2010 and in the United States on November 20, 2010.
After our Heroes dock on Lily Of The Valley Island for the Sinnoh League competition, Ash completes his registration and calls Professor Oak to thank him for the good-luck flowers and card. Ash also asks the professor if he will send the Pokémon he’s been keeping for Ash at his lab, and Professor Oak happily agrees.
Team Rocket, as usual, has a plan to steal Ash’s Pokémon, and grabs five of them during the transfer. The villains are soon sent blasting off again, but Ash’s Poké Balls go flying as well!
Our Heroes quickly find the Poké Balls, but they’re empty! So our Heroes set off to find Ash’s missing Pokémon. One by one, Corphish, Totodile, Snorlax, and Bayleef are all found safe and sound.
Team Rocket isn't through yet, though, and they go after Ash’s last missing Pokémon, Cyndaquil, with a seemingly invincible robot! During the battle, Cyndaquil evolves into Quilava, and uses its newly learned Eruption move to send Team Rocket blasting off a second time.
As the opening ceremonies begin, Ash notices that Nando, Barry, and Conway are all competing—as well as Paul. And so, as he looks forward to his first-round battle against Nando, we leave Ash at the beginning of the next chapter in his continuing journey to become a Pokémon Master!
Ash and his friends make their way to the Trainers accommodation. While Dawn admires the setup, she feels a sudden chill and turns around to see Conway standing there. Ash and his friends learn that Conway is also participating. Inside, Dawn and her Piplup instantly take a liking to the bed while Ash notices a basket with a note from Professor Oak. Ash immediately contacts the Professor via videophone and requests some of his reserve Pokémon to train with. Dawn is clearly excited to see some of Ash's other Pokémon onscreen, with Muk instantly smothering Professor Oak with affection. Ash prepares for the transfer, exchanging his current party, save for Pikachu, for others.
In the opposite room with the Poké Ball transfer machine, Team Rocket pose as the operators, securing Ash's Pokémon. They take the five Poké Balls and leave the room, claiming to be examining them. Outside, Meowth rolls up in a Golf Cart. Ash and his friends wait, becoming uneasy, as the real operator shows up, revealing to Ash and his friends about the imposters. Outside, Ash and his friends confront Team Rocket who attempt to flee, but Pikachu's Thunderbolt sends them flying, along with Ash's Poké Balls. Dawn follows their descent and leads Ash to them. Unfortunately, all five Poké Balls are open and empty when they reach them.
They begin to search for the missing Pokémon. Immediately, Ash spots his Corphish wandering around, while nearby, his Totodile is playing in a fountain. Ash calls to his Pokémon and they immediately run towards him. Corphish shows him affection before Ash puts it in the Poké Ball. Ash gets up just as Totodile lands and Bites his head, before hanging onto his shoulder, Ash happily recalling it. At a nearby kitchen, Ash's Snorlax proceeds to eat all the food, much to the dismay of the cooks. Ash finds Snorlax and scolds him for eating food that isn't for him, and apologizes to the chefs. Snorlax pulls Ash's Pikachu off of his shoulder and licks him affectionately before Ash recalls it. After recalling Snorlax, however, he realizes he never asked Professor Oak to transfer it across. Back in Kanto, at Professor Oak's Laboratory, the Professor realizes he has made a mistake when he notices that Ash's Heracross is still there, getting sap out of Bulbasaur’s bulb.
Meanwhile, Ash continues to search for his Pokémon when he spots Barry walking towards him, holding his head. Noticing the bump, they ask what happened. Barry recounts being tackled from behind by an unknown Pokémon, unable to identify it, but noted that he could smell something spicy. Ash believes he knows which Pokémon it is. Barry immediately holds Ash accountable since he revealed it was his Pokémon, but Ash and his friends run off. Ash calls out for the Pokémon, and it hits him from behind. It is his Bayleef, and she shows clear affection for Ash. Ash tries to recall her, but she takes the Ball out of his hands, wanting to stay outside. Now, they have to search for only one more.
Back at the living quarters, the last Pokémon, Ash's Cyndaquil is confronted by Team Rocket in a mecha. Cyndaquil flees as the mecha tries to strike. It then fights back with a Flame Wheel, dodging the mecha arms and accidentally setting a tree on fire. The smoke gets Ash's attention as he and his friends race over there. They see the situation and Ash has Corphish and Totodile put out the fire, along with Piplup's help. Bayleef launches Razor Leaf to cut off the mecha's arms while Pikachu launches a Thunderbolt, but the electricity is ineffective and the mecha replaces its arms. Cyndaquil hides behind a tree while Bayleef fires another Razor Leaf, but the mecha's chainsaw arm blocks it. Ash calls out Snorlax, but it is sound asleep. Ash tries to wake it by pushing it, but it falls over, knocking the mecha down. The Water Pokémon fire attacks at the mecha, dowsing it in water, while Pikachu fires another Thunderbolt, but that fails. The mecha flies into the air as Cyndaquil comes out to battle, firing a Flamethrower. The mecha takes it and spins, sending fireballs raining back down. Cyndaquil scurries to dodge the mecha’s arms, but it gets cornered by a boulder. Meowth has the mecha grab Cyndaquil, who unexpectedly evolves into Quilava. Ash checks it with his Pokédex as Quilava fires up its flames, darting underneath the mecha and using a new move, Eruption, to destroy the robot and send Team Rocket blasting off. Ash is amazed at Quilava's strength.
Later on, Ash talks to Professor Oak as he proceeds to train with more of his Pokémon. His Glalie, Torkoal, Noctowl, Muk and Donphan get time to train. Later at night, the opening ceremony for the Sinnoh League kicks off as all the participating Trainers and spectators gather in the coliseum, watching the torch be lit among the fireworks. Ash looks around and notices familiar faces in the competition: Nando, Conway, Barry and Paul. The main screen shows the first round pairings, and Ash's first match is against Nando.
When the four stadiums are lit up towards the end of the episode, one can see the colors blue, red, and green, all of which were connected to the middle stadium, which is yellow. These represent all of the Generation I games.