No Easy Way - S1-E12
Other mistake: Morisaki is the substitute keeper, but he has the number 1 jersey (See next episode for an explanation about this part being prolly a mere continuity error). He also did not appear in the tryouts or the previous matches. He is wearing the Nankatsu Elementary school jersey but it's supposed to be a different character from that keeper - incidentally, in the match against Shuutetsu that keeper did at least a great save, better than anything Morisaki is able to do in these early episodes.
Other mistake: There were 3 defenders not taking part to the birdcage strategy, but Tsubasa does not have to beat any of them, except Takasugi who tries an American football tackle that would be penalized even by the very loose standards of the referees of this anime, and that happens as if he had to intercept him coming from behind; by every logic he should be in front of him. (00:20:55)
Other mistake: Roberto meets Genzo at the shrine in the early morning, and Genzo is pumped up and ready to go to the match. In another scene, Roberto is at the stadium hanging out on his own, but Genzo still hasn't got to the stadium and will arrive only much later when the match is about to begin.
Other mistake: Eleven Nankatsu players run past the 4 Shuutetsu guys who are looking for Genzo. They all wear the team jersey, the keeper is missing. They have just players total, 10 plus the keeper, the extra player was never supposed to be there. (00:04:05)
The Football Is My Best Friend - S1-E4
Other mistake: Tsubasa is quicker and much more skilled than his friends with the ball and took off much earlier too, but they reach the crosswalk at the same time. (00:04:10)
The Football Is My Best Friend - S1-E4
Other mistake: When Roberto tells everyone that they should try to treat the ball like their friend (except when they kick it, arguably) one of the kids who react with puzzlement at this unusual statement is Tsubasa, but he is the one character who already does that ordinarily as established in previous episodes. (00:02:40)
Other mistake: Tsubasa is talking to 'his friend' the football as he does keepie-uppies. He is normally animated pretty decently during that activity, except in the shot when he is telling his friend about Genzo's skills; he is keeping his torso completely immobile, moving just his thighs, which is just physically impossible. A few shots later his torso is still again but at least his thighs are not in frame (the ball is though, what could he possibly be using to juggle it up?). (00:06:10)
Other mistake: The international dubs (Spanish, Italian, from what I understand even Arabian) have the narrator say that Fujisawa (which is where the international dubs set the story instead of the fictional town of Nankatsu) is renowned for its football teams, plural. That's not true, since the only strong team is Genzo's Shutetsu, and the competing team in the local derby loses 10-0 to them, and the prestige the city has comes from their victory in the previous championship tournament.
Other mistake: Star keeper Genzo Wakabayashi has a trademark hat with his name and a cool logo. According to his manga character design he was supposed to wear the Adidas logo, but copyright issues arose and the Nankatsu logo is a great substitute visually - sadly it makes no sense, because he is sporting it already at the beginning of the anime and the team with that logo will be properly formed only later in the series.
Other mistake: After his ankle injury from the previous episode, Ryo writhes in pain touching...his knee. (00:03:00)
Other mistake: The linesman's flag as he hands the ball to Taki is unreasonably tiny. (00:18:45)
Other mistake: Masaru falls into the river and Tsubasa follows him getting knee-deep and with socks and shoes on, but the moment they step out of the water both are perfectly dry and have no problem or discomfort at all. (00:07:20)
Other mistake: In the Italian dub, Ryo ("Bruce Harper" as he is known in international versions)'s mom yells at him for running away with the football...but Ryo is not carrying any ball. (00:05:05)
The Football Is My Best Friend - S1-E4
Other mistake: In the opening shot of the dinner scene, Tsubasa's soccer ball is on the chair next to him and as logic dictates it is below table level. Later though it is much higher. Conversely, Roberto's head in other shots is so low that looks like he's sitting on the floor. (00:04:45)
Other mistake: Needless to say, having a football on your belly can't cushion the impact with a truck. Even forgiving this obviously cartoonish impossibility, still the way Tsubasa lands looks all kinds of wrong, with the forward momentum instantly halted as the ball touches the ground again. (00:14:25)
Other mistake: Only one of the keepers from Meiwa FC appears in the episode; Wakashimazu replaced another one who is nowhere to be seen.
Other mistake: Jun's parents can't see the kids by the goal, only their shadows, but they are positively unfazed when Tsubasa is celebrated loudly and dangerously acting as substitute for him (which is the reason why Tsubasa is replacing Jun in the celebration to begin with).
Other mistake: In the previous episode it was established that the final takes place the day after the semifinals. The kids went right away to the hospital and talked about the match against Musashi, wearing normal clothes, and had a night adventure searching the town left and right. In this episode another day passes by before the final.
Other mistake: When Tsubasa is staring at Urabe running in the distance, Urabe's hair is see-through in some shots and you can see the shape of his skull (or at least a glowing circular spot that appears in some frames only). (00:11:05)
Other mistake: When Misugi is on the ground in pain after Tsubasa's equalizer, one of the forwards is watching him, but the number 10 on his jersey is transparent. (00:09:25)