The Games That Play Us - S1-E22
Other mistake: In the last episode of season 1, Lucas goes to see Haley and Nathan where they tell him they got married last night, which must have been after the playoffs game. However, in season 2 in flashbacks of their wedding they got married during the day.
Other mistake: When Sportacus jumps out of his blimp, his crystal is missing.
The New Kid - S1-E2
Other mistake: At the start when the gang change the time on the clock in the classroom, it wouldn't control the main school clock, plus in every other episode the clock has been operated by The Box on the side of the school, as shown in " The spy who came into the playground".
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.
Other mistake: Throughout the episode, characters make reference to Mark's Grandma having a wooden leg, including the woman herself. However, both of her legs are visible from the knee down several times in the episode, and you can see both of them are flesh and bone.