Flower Power - S3-E6
Factual error: During the second battle with Team Rocket, Arbok and Victreebel use Tackle, a move they cannot legally learn in the games. (00:18:15)
Suggested correction: Differences between anime and games are not mistakes.
So Near, Yet So Farfetch'd - S1-E47
Continuity mistake: When Team Rocket takes off in the boat, it sinks. Their pokeballs float away, and Jessie says "Arbok and Lickitung are floating away!" But she doesn't catch Lickitung until Princess Versus Princess (Season 1, Episode 52).
Suggested correction: It's because these episodes were aired out of order.
Character mistake: When Mandi brings out Golbat, Brock says, "Kingler is really weak to air attacks." But Kingler's a Water type, which has no weakness to Flying-type attacks.
Suggested correction: Brock is saying that Kingler is vulnerable to attacks from the air, not that it is weak to Flying-type moves.
Continuity mistake: When Ash says, "Misty'll take good care of your Marill, you'll see," Wilhomena is holding her parasol with on hand, but in the next shot, she is holding it with two. (00:09:16)
Suggested correction: I rewatched the shots, and Wilhomena is holding her parasol with both hands in both of them.
Mystery at the Lighthouse - S1-E13
Other mistake: When Brock turns his head to the costume, his nose is missing. (00:12:47)
Suggested correction: Agree with the other correction. Dropping details, such as facial features like a nose or mouth, and simplifying character designs is a very common and encouraged drawing/animation technique to imply distance. This isn't something the animators would just overlook. It was a deliberate decision. Ash and Misty similarly look somewhat less detailed than they do in closer shots. At best, this would be a deliberate mistake, but I personally think it falls under the umbrella of "suspension of disbelief" and shouldn't be considered a mistake given it's a stylistic choice to imply distance.
Suggested correction: His nose isn't seen because he is far away from the camera.
Pokémon Contest! Hajitsuge Convention! - S7-E10
Factual error: During the battle with Team Rocket, Beautifly uses Tackle. However, it was unable to learn it until Generation VIII. This episode, a Generation III episode, would mean that at this point in time, Beautifly was unable to learn it by any means. (00:19:57)
Suggested correction: Differences between anime and games are not mistakes.
Factual error: During the second battle with Team Rocket, Victreebel uses Tackle on Ash and his friends. However, it cannot legally learn it in the Pokémon games. (00:18:18)
Suggested correction: Differences between anime and games are not mistakes.
Chicorita's Jealousy!? - S3-E20
Continuity mistake: At the beginning of the episode, Chikorita is inside a pipe, but in the next shot, the pipe vanishes. (00:01:16)
Suggested correction: I watched the shot and Chikorita is not in the pipe to begin with.