Continuity mistake: When Sam is surprised by what he sees after he first stops running, his bag's right strap is not beside his collar, but in the next shot, it is. (00:06:08)
Continuity mistake: When Sam thanks Towa for her gift, the rock to the right of Towa and the tree to the left of it are there, but in the next shot, they disappear. (00:04:30)
Continuity mistake: When first showing the parting gift, Towa's left thumb is in between the top and the bottom of it, but in the next shot, it is at the top. (00:04:21)
Continuity mistake: When Towa tells Sam to wait, the rock closest to the left of her and the rope on change design, and the trees behind them go from being present to being absent. (00:04:13)
Continuity mistake: When Sam asks, "Time travel?" Towa's necklace is not on a violet part of her robe, but in the next shot, it is. (00:03:52)
Continuity mistake: When Sam says that he has never heard about the Voice of the Forest, Towa's necklace is on a violet part of her robe, but in the next shot, it is not. (00:03:47)
Continuity mistake: When Sam is crouching while his sketchbook is on the ground, the cracks on the rocks change between shots. (00:07:22)
Continuity mistake: When Towa says that Sam should not tell anyone about the Voice of the Forest if he hears about it, her right hand is on her apron, but in the next shot, it is on her robe. Also, the rock closest to the front of her has no crossing of ropes in front of her, but in the next shot, it has one. (00:03:41)
Revealing mistake: In the shot where Celebi calls for help, its shadow disappears before it leaves the screen. (00:05:28)
Continuity mistake: When Sam is amazed by the power of time travel, the trees behind him change between shots. (00:03:59)
Continuity mistake: When Celebi shakes on the ground, the flowers around it change between shots. (00:05:03)
Continuity mistake: In the recap, in Pikachu's Poké Ball's receiving, the tiles are larger in the movie than in the episode. (00:01:53)
Revealing mistake: When Professor Oak is getting a book from a bookshelf, the book appears out of nowhere. (01:15:52)
Character mistake: When they find a Suicine, they ask Oak and he says it's a Swecon.
Suggested correction: I watched the film, and Professor Oak pronounces Suicune's name correctly.
Continuity mistake: In the shot where they first visit the Lake of Life, Sam wades into the water (all the way up to his waist). As he steps out, there is only water at his ankles, and moments later, there is no water. (00:34:56)