Showdown in Pewter City - S1-E5
Continuity mistake: When Ash and Misty turn to Flint at the Pokémon Center, the left strap on Ash's rucksack is blue while the part of his jacket to left of it excluding the sleeve is green, but in the next shot, the strap is green while the part of his jacket is blue. (00:03:55)
Showdown in Pewter City - S1-E5
Continuity mistake: When Flint tells Ash to come with him, Ash's gloves disappear. (00:08:15)
Showdown in Pewter City - S1-E5
Continuity mistake: When Team Rocket is wondering where the trap is, Jessie's right glove changes from black to skin-colour. (00:01:46)
Showdown in Pewter City - S1-E5
Continuity mistake: When Ash says, "That's a great idea!" Flint's right arm is turned towards his right side, but in the next shot, it is turned forward. (00:10:12)