The one episode I really want to see is similar to one of the movies, Charizard sees Ash in trouble on TV, and rushes to his aid, only, Ash somehow has no usable pokemon at the league (All were weakened by Team Rocket or something) and is unable to transfer due to computers being down or something, and is told if he doesn't have pokemon to use in the next hour, he'll be disqualified. The hour is just about to run out when you turn and see Charizard, Pidgeot, Butterfree, carrying Primeape, Lapras, and Squirtle onto the field, willing to fight. XD
Could even have a story for all of them.
Delia runs to Viridian Forest to tell Pidgeot, and happens upon Primeape on the way to get to ash, who is carried by Pidgeot. Charizard is alerted by Liza that Ash needs help, and he takes off to help, stumbling upon Lapras in the ocean on the way, who also leaves it's group temporarily to help. (Chari would carry her after it reaches the shore, XD) Squirtle is being sped there by Officer Jenny when he spies Butterfree overhead, who is more than willing to help, and carries Squirtle in the air, to go faster.
It's a total fanfic thing, never would happen, but I think it'd make an amazing final battle vs Paul. All of the Pokemon he released so they could be happy fighting to make his dreams come true. XD I think it'd be a great way to release Ash from the anime. :P
I really wish they'd stop doing things like mentioning ash's old pokemon are returning in titles, etc. I keep hoping that means Butterfree ._.