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: Tsubasa's mom calls him because the movers' truck is leaving. He kicks the ball outside the window, and is downstairs to catch it, quite the impossible feat especially when you factor in that he kicked the ball with not much of a vertical trajectory, almost in a straight parabolic pattern out of the window, and meanwhile he also found time to wear and fasten his shoes. And it's not even played up as something strange. (00:03:00)
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)
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: Genzo's challenge invites anyone to score shooting outside the penalty area...but we see that at least the rugby captain is standing inside the box. (00:12:20)
Other mistake: When Tsubasa kicks the soccer ball returning Wakabayashi's shot, the ball goes under the lorry and flies past several drive shafts. (00:21:50)
Other mistake: Tsubasa 'powers' in this episode get nerfed in the rest of the series; he is in elementary school and yet his shot flies literally miles off to land with precision in the arms of Wakabayashi. If he had this power and precision during a match, he'd be superhuman.
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: 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: 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: When Miss Ozora tells Roberto that he should have shown her The Letter from the beginning, Tsubasa is drawn looking in the wrong direction. (00:17:25)
Other mistake: When Sanae tells to the team "Ishizaki is right!" and gives them a pep talk, she's practically a hobbit next to the others, and a couple players are on odd mounds as if it were a baseball field. On a soccer pitch you just can't have that sort of uneven ground. (00:19:00)
Kick-Off for the Future - S1-E3
Other mistake: Spurred by his new deskmate, Tsubasa juggles the ball and sends it with a header right onto the empty seat. Pretty sure it's forbidden in any school to just come to class with a football, but besides that; look at how the football is in view. How tall would the chair have to be for that to happen? Whoever sits on it has no room to put their legs under the desk for sure. (00:10:35)
Kick-Off for the Future - S1-E3
Other mistake: When Manabu is approached by the bully, his glasses in close-up lack the bridge. (00:13:40)
Kick-Off for the Future - S1-E3
Other mistake: The kid who wants the soccer team to stop training is told off by Sanae, who points at the good efforts on the pitch. The animation of the team in training has noticeable errors, with a player that suddenly appears coming out of nowhere from behind the rightmost one, who is standing immobile in front of the goal and after a second disappears abruptly. (00:14:05)
Kick-Off for the Future - S1-E3
Other mistake: Urabe mentions that Nankatsu lost to Shutetsu 30 to 0 (which seems rather uncanny for a 40 minutes match), but the score mentioned in the first episode was 10 to 0. The more extravagant result ends up being the canon one.
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)
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: 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)
The Football Is My Best Friend - S1-E4
Other mistake: In the opening longshot of the Shuutetsu sparring match with Mizukoshi, the side on the right has 10 players instead of 11. (00:07:15)