The March of the Exeggutor Squad - S1-E41
Other mistake: The Pokemon Exeggcute is shown evolving in to an Exeggutor naturally. But the Pokemon Exeggcute can only evolve into an Exeggutor with the use of a leaf stone. In the Japanese version, there is a mention that something in these woods causes Exeggcute to evolve without using the Leaf Stone (when Exeggcute evolves, James even mentions that there is no stone). However, as this was skipped in the English version, it creates a plot hole.
Other mistake: Assunta's Ivysaur attacks Sparky too early, before the battle even started, not to mention Assunta haven't given it any commands during the battle.
Mystery at the Lighthouse - S1-E13
Other mistake: When Professor Oak goes to rotate his monitor, his right index finger is intermittently not coloured in. (00:09:15)
Pokemon, I Choose You! - S1-E1
Other mistake: When Pidgey turns its head to see Ash with a Poké Ball, its head feathers beside its eyes are mistakenly coloured cream instead of brown. (00:11:36)
Bulbasaur and the Hidden Village - S1-E10
Other mistake: In the scene when Team Rocket tries to steal the Pokemon, Bulbasaur saves Oddish. Ash comes to help push Bulbasaur, and for a few frames you can see 2 sets of hand prints cut out where Ash's hands go.
Abra and the Psychic Showdown - S1-E22
Other mistake: When Ash says, "Without a Marsh Badge, I can't get into the Pokémon League!" the strips on Pikachu are missing. Also, Ash does not have gloves, but in the next shot, he does. (00:07:11)
Mystery at the Lighthouse - S1-E13
Other mistake: When Ash and friends are first seen walking on a path, Pikachu's cheek pouches are missing. (00:01:14)
Other mistake: When the camera pans across the Pikachu when they are surprised, one of them is missing its cheek pouches while another is missing its left one. (00:03:06)
Other mistake: When Ash and friends are first seen when a Ghost Pokémon laughs, the base on Pikachu's tail is missing. (00:07:47)
Other mistake: When Brock says, "Yeah. The season of love is when Butterfree lay their eggs," two Butterfree occasionally are missing feet, and another one occasionally has a part of its wings mistakenly colored black instead of white. (00:01:49)
Clefairy and the Moon Stone - S1-E6
Other mistake: When the camera begins panning back to show Seymour, Ash, Butterfree, Zubat, and Brock, Pikachu's mouth is missing. (00:11:18)
Other mistake: When Ash, Misty, and Brock are worried about the cyclone approaching, the edges of Meowth's ears are mistakenly colored tan instead of black. (00:20:08)
Other mistake: When Pikachu's pain increases, his nose is missing. (00:01:51)
Tentacool and Tentacruel - S1-E19
Other mistake: After the Tentacool on Meowth says that Horsea must be punished, Meowth's mouth is missing. (00:14:38)
The Ninja Poke-Showdown - S1-E32
Other mistake: When the floor in the slanted room tilts, Ash and his friends tilt, but the trapdoor does not. (00:15:19)
Other mistake: When Todd says Ash and his friends are on time, his camera is in front of them despite him hiding from the side. (00:13:09)
Island of the Giant Pokemon - S1-E17
Other mistake: When Ash and his friends are about to hit the Zapdos robot, its body is missing, and shortly after, Pikachu's cheek pouches disappear. (00:18:42)
Island of the Giant Pokemon - S1-E17
Other mistake: When Jessie says she cannot stand roller coasters, part of the background is coloured in like her hair. (00:17:26)
Island of the Giant Pokemon - S1-E17
Other mistake: When Ash wakes up on the beach, part of the sides of the hat overlaps the front. (00:01:53)
Pokemon, I Choose You! - S1-E1
Other mistake: When Ash gets Pikachu's Poké Ball from Professor Oak, the latter's hand right hand is drawn backwards. (00:06:52)
Answer: Yes it ran away because Layla hurt its feelings.