Ghoul Daze! (Japanese: 放課後はゴーストタイムIt's Ghost Time After School) is the 90th episode of Pokémon the Series: Diamond and Pearl, and the 556th episode of the Pokémon anime. It first aired in Japan on August 21, 2008 and in the United States on January 17, 2009.
On the fifth day of the Pokémon Summer Academy, Professor Rowan has a special assignment for his campers: they'll each team up with a partner and go to the Summit Ruins at night. They're sure to meet Ghost-type Pokémon along the way, but the first team to retrieve the Summit Ruins medal will win! Ash and Angie team up, while Brock's partner is a nervous kid and a macho boy named Kendall wants to be Dawn's partner. Conway's partner is a strange little girl. That night, the teams enter a forest on their way to the ruins, but Conway's partner doesn't seem to be anyone from the Summer Academy...
Ghost-type Pokémon try to spook Angie's Shinx, but Pikachu shocks them into leaving it alone. As for Dawn, her partner runs away as soon as he sees the Pokémon! Conway's partner turns out to be a ghost who hypnotizes him into walking off a cliff, but a Dusknoir appears just in time to save him! Unfortunately, he faints before he has a chance to realize Dusknoir is one of the good guys.
Dusknoir also saves Meowth from the ghost girl, but now everyone thinks Dusknoir is the real menace. According to Professor Rowan, there shouldn't even be a Dusknoir here, unless it emerged from the mysterious cavern discovered in the Summit Ruins.
Ash and Angie reach the Ruins and find the Summit Medal. They've also found the ghost girl—so when they see Dusknoir, they battle it to protect the girl. Big mistake: the girl opens up a swirling portal to the spirit world and tries to suck in Angie and Ash. Dusknoir wakes up in time to save them and blast the ghost girl back into the cavern, which collapses behind her. Everyone realizes that Dusknoir was really trying to protect people from the ghost! Now that she's gone, things return to normal and Professor Rowan awards everyone equal points. That's the end of another day at the Pokémon Summer Academy!
While Ash and his friends are at the Pokémon Summer Academy, their third lesson is on how to correctly approach Ghost-type Pokémon, when ever and where ever they encounter them. They are then paired up to find a hidden medal in the Summit Ruins. The medal and how fast it's retrieved is needed to get points for the activity. While searching for a partner, Conway has a run-in with a mysterious girl, and is put into a trance. Meanwhile, a boy named Kendall asks to join Dawn, telling her that he'll protect her from Ghost Pokémon. Ash and Angie also pair up, while Brock partners with Mitchell. On the night of the event, the paired-up Trainers head to the Ruins, when a girl is discovered to have been left behind. This alarms Professor Rowan's female assistant who had seen the 10 Blue Team members off moments before.
The Trainers encounter Professor Rowan's tame ghost Pokémon, and handle the situation differently. A Haunter grabs Shinx, and Pikachu attacks it, but Ash apologizes, and they go on their way. Brock, however, gives the Ghost Pokémon some food, and gets safe passage. When Dawn and her partner Kendall come across eating sounds, Kendall fear's he'll be eaten (next) and runs away in fright. Afterward, Dawn sees Conway walking and no partner. She goes to investigate just as Conway is coaxed towards a cliff by the ghostly girl. Conway is about to walk off the cliff when a Dusknoir grabs his arm, waking Conway from his daze. Though safe, Conway faints at Dusknoir's appearance. Dawn stumbles upon Conway on the ground, with Dusknoir ominously overhead. Dawn misinterprets the scene as Dusknoir has hurt Conway, and she confronts it yelling, "Alright, what did you do to Conway?!" The Dusknoir exclaims and waves its arms before fading away. Dawn rushes up and wakes Conway. Conway explains to Dawn that he was following a girl, and according to what the Pokédex said about Dusknoir, Dawn and Conway incorrectly assume that Dusknoir took the ghostly girl to the spirit world, and was about to take Conway too.
Meanwhile, Meowth attempts to scare Ash and Angie, but incapacitates himself after literally zipping his lips in a Banette disguise's zipper mouth. Missing his opportunity, Meowth continues to attempt to unzip his lips, when a real Banette helps him. Thanking the Banette, Meowth realizes he's surrounded by Ghost Pokémon, scaring Meowth off. After he reaches safety, Meowth is lured by the girl with food, but is stopped by Dusknoir. Meowth starts yelling, but then gets scared when he realizes it's a Dusknoir. Like Conway, Meowth is scared into fainting, and discovered by Jessie. Jessie is then confronted by Dusknoir. Jessie freaks out and drops Meowth, then runs away leaving Meowth and her partner behind. Jessie runs past Brock and Mitchell, with her partner behind her carrying Meowth. Brock and Mitchell wonder what had scared them away, but then they too are approached by Dusknoir. Brock tries offering some food to the Dusknoir, but the Dusknoir rejects the food and uses Will-O-Wisp at them. After Brock and Mitchell run away, Dusknoir spots the ghost girl in the bushes nearby.
Jessie and the others run back to the Academy, and report about the Dusknoir, as Ash and Angie meet a Misdreavus. Misdreavus uses Screech, and makes Ash and Angie run away and get lost. The girl appears and then beckons Ash and Angie to follow her, while the others have made it back to Professor Rowan. Being that Pokémon in the area are monitored and documented, the reports of a Dusknoir is alarming to Professor Rowan, especially since Dusknoir is a forest-dwelling Pokémon with no need to be in the area. Rowan also explains that an accident occurred one day when a mysterious cave was uncovered behind a wall. He also states that it might be the entrance to the spirit world, and that he assumes Dusknoir is trying to take someone there. Conway tells Rowan that he followed a girl and he thinks Dusknoir has taken her away.
It is concluded by Professor Rowan that the Dusknoir must have originated from a mysterious cave, which is thought to lead to the spirit world. Meanwhile, Ash and Angie finally get to the Summit Ruins, and get the medal first. There, the girl tries to coax Ash and Angie into the cave Professor Rowan mentioned, when Dusknoir appears. Dusknoir prepares to attack the girl, but Ash and Angie battle Dusknoir to protect themselves and the girl. Pikachu and Shinx attack while Dusknoir's back is turned on them. Dusknoir is momentarily stunned, and the girl tries to suck them into the spirit world through the cave. Angie is pulled into the air, but caught by Ash who holds onto her. Meanwhile, everyone arrives at the spot, and Professor Rowan prevents anyone else from getting too close. Dusknoir gets up and grabs Ash and Angie, then sticks its tail into the ground to keep from getting sucked into the portal. Ash and Angie are shocked and realize Dusknoir was trying to protect them all along.
After a few moments, the portal starts to drag them closer, with Dusknoir's tail moving through the dirt. Ash and Angie freak out, and Dusknoir turns around and blasts the girl, collapsing the cave entrance. After everyone thanks the Dusknoir, the Dusknoir flies off and disappears. It turns out that the girl was a ghost and Dusknoir was trying to stop her. Conway panics at the fact that he was partnered with a ghost the whole time. The next day Professor Rowan awards each team 30 points for a job well done. None of the teams gained an advantage, and the Blue Team leads by 260 to the Red Team's 220. Ash isn't discouraged as he rallied for the Red Team to turn the tables and takes the lead.
Ghost types introduced in each of the four generations appeared in this episode.
Similar to the previous episode, this episode also features scenes of hypnotic trance.
In one scene, Ash mentions to Pikachu to just count to ten when a Haunter grabs Shinx's tail and Pikachu zaps it. This could refer to a Japanese myth about a ghost who is unable to count to ten, then suddenly disappears. It could also refer to the common teaching in America to control anger.