The only big continuity error I can think of is Stormy Weather's line about the episode being on the first day of Summer. There's just no way it works when Origins made it clear that the show started when school for the year did. I chalk it up to something that wasn't corrected when Origins was released.
>>98107196*Origins first
*Volpina at the end of Season 1; Collector immediately after
*Evillustrator after Stormy Weather and Lady Wi-Fi
*Puppeteer after Evillustrator, Lady Wi-Fi, and Rogercop
*Antibug after Guitar Villain
This is literally the only continuity Season 1 has. Anything else like calendars in the background that are only there for one-off jokes (like the "Adrien schedule") are to be disregarded.