I got to watch it today, so...
+ Carnival; Brock takes care of a stall for the fisherman, I think? So, yeah, he basically just sits there with his Pokemon doing nothing. TR's Goldeen catching stall had a lot of visitors.
+ Johanna said something like "Kurotsugu to mama tomodachi ne" or something like that, keyhole crapped out during that time, which means 'Palmer and mama are friends'...?
+ Very very short battle, which was Heracross vs Pikachu, but they got interrupted when Barry saw Xatu flying.
+ Ash, Barry & Dawn follow Xatu to a tent, where a man asks them to go in, and thus the weird illusions begin. At least, I think it was illusions.
+ Everyone got seperated from their Pokemon. Ash sees a 'gigantic' Nidoking, Nidoqueen and some bug Pokemon, and then his past experience with Spearow begin. Dawn sees a 'gigantic' Fearow, a Feebas & a Magikarp. Ariados appears. Both Pikachu & Piplup save their trainers respectively. Barry's past experience was shown as well. They reunite.
+ Natu glows and the 'illusion' ends, and the tent disappears. The Xatu flies overhead again.
+ Barry gets up and bumps into Palmer. Palmer is confirmed to be his dad as Barry says "Daddy??" after seeing him.
+ They return to Twinleaf Town.
And that's about it. In the preview, Empoleon is seen battling with Pikachu; Rhyperior vs Grotle.