Continuity mistake: When Michelangelo loses consciousness and his helmet, the helmet rolls on the ground above his head, but when the rebels are approaching to pick him up and haul him on the cart the helmet is by his shoulder. (00:26:10)
Continuity mistake: When Michelangelo shouts "Woah! Good horsey! Good horsey!" the scepter goes from his left hand to his right between shots. (00:25:35)
Continuity mistake: Walker witnesses the music playing and the guards wrecking the demonic machine; he constantly has his left hand held up in the air in the close-ups, but in the other angle he shifted that hand to lean against the door. (00:15:45)
Audio problem: April's walkman keeps playing for a while spreading in the air the suave notes of The Barrio Boyzz's "Conga" even when the batteries already came out on the first strike. (00:15:40)
Continuity mistake: April's walkman is very conveniently prone to play randomly. She puts it down on the floor, but it is, together with the headphones, positioned differently practically at every shot in particular when the guards start bashing it and everything is closer together in close-up than in wider angles. (00:15:30)
Continuity mistake: In the sequence set in present time when the Turtles interact with Kenshin, once he faints seeing the giant Japanese-speaking rat the shopping bags on the table changed position - the blue bag the wind knocked on the floor is back, and the red bag is up and not horizontal. (00:12:00)
Continuity mistake: Leonardo shouts "He's a man!" when Kenshin appears in the Turtles' hideout; he is holding in the foreground with the right hand his book about katanas, but in the next shot it's on the table, under his left hand. (00:11:35)
Continuity mistake: April materializes in the same spot as Kenshin; her headset is placed away from the collar of the kimono. She is still in the same position when she spots the priest, but the collar is underneath the headphones now. (00:11:50)
Continuity mistake: Kenshin throws a temper tantrum in a room with several statues. The doors open and a strong wind blows; the position of the scrolls on the table changes between shots; they are first closed by the edge of the table, then unfurl from a position much further behind. (00:10:10)
Continuity mistake: Walker's henchmen dump on the court Lord Norinaga's sentinels and walk away. They are already shown posing with evil smirks and all that in the next shot while Walker is doing his threatening speech. (00:08:55)
Continuity mistake: We first see Lord Norinaga in a close-up looking at his son's arrival. His helmet is tied under his chin, but when he walks in the helmet's cord is split above and below the chin. (00:07:40)
Other mistake: When April O'Neil arrives bringing gifts, she leaves the manhole cover completely open - there's also an awful lot of light coming from there, as if the abandoned subway station were built inches away from the surface. (00:05:20)
Continuity mistake: During the introduction of the turtles, Michaelangelo's bandana goes from the back of the shoulder to the front and then both ends behind the shoulders between shots. (00:04:30)
Continuity mistake: Kenshin loses his sword battling with the guards at the beginning of the movie. The sword gets stuck almost horizontally in a tree stump. Then one of the guards grabs it as he rides by with his horse, but the katana is now stuck in the tree at a sharper angle which makes it possible to reach for it and grab it on the fly. (00:02:35)
Continuity mistake: When Benkei climbs the sewer ladder and disappears into the light, Donatello is touching the ladder in the first shot, in fact he puts both hands on deliberately, but he's not even touching it in the second. (01:28:35)
Other mistake: When the Turtles start their time travel, it's night in Japan. Almost 60 hours pass, and it's again nighttime in Japan.
Revealing mistake: Walker meets his demise in sequence with a shockingly poor visual effect; he falls into the ocean from the cliff, and instead of splashing into the water, he sorta disappears quickly through it. (01:22:55)
Factual error: During the movie, characters may use lingo that would not be understood easily in the time period of their counterparts. April for instance uses the word "cool" in the modern sense, and nobody questions that, but you could assume that they don't understand every word and infer nonetheless the meaning from the context. Walker however when he's about to fire his cannon uses an idiom "Try this on for size" that was coined in early XX century. (01:19:40)
Continuity mistake: In the baffling phase when Whit takes exception to the killing if it's done by guns and Walker just throws him with the others, Elias Koteas moves his gun from the left to the right hand when Stuart Wilson calls for Niles, but in the next shot the gun is much lower. (01:18:15)
Plot hole: The plot takes a turn for the nonsensical when the Turtles find the Scepter and Mitzu walks off. With no explanation (she is the best fighter of the resistance) Whit captures her. There's no explanation on how he did it with such ease, how did he happen to be at the right place at the right time since nothing of what happened was under his control, and even where this 'right place' was, because he is riding towards the village (and the Turtles themselves) with her - just how far did Mitsu wander during Grandpa's very short apology to be captured by someone who gallops to the village to show her off as bargain chip? (01:05:45)
Answer: It might just be incidental music, but it sounds more like a variation of "Yoshi's theme" (an original score for the film), which was meant to sound like traditional Japanese music.
Bishop73