Continuity mistake: In 'Morality Bites', Phoebe has her premonition about being executed while watching a news report on a baseball player, right after she and the others punish Pratt. When she returns in time at the end of the episode, they all watch the news report first and only afterwards look out the window and see Pratt. (00:02:10 - 00:39:50)
Continuity mistake: Phoebe was the first to get out of the kitchen, then Piper followed, and last was Prue, but when we see them running to the window, Phoebe is first, then Prue then Piper. (00:00:40)
Visible crew/equipment: While Phoebe begins her "fifteen minutes of channel surfing" she has the burning premonition and cries out, then in the next shot as Prue and Piper rush in, we can see the reflection of the boom mic/pole in the wall mirror. (00:02:10)
Factual error: Phoebe is going to be burned at the stake for witchcraft like they're starting the Salem witch trials again, but witches weren't burned, they were hanged.
Continuity mistake: When Prue, Piper, and Phoebe return from the future, Prue and Piper hug Phoebe in relief. In the following shot, Piper wraps her arm around Phoebe again. (00:39:20)
Visible crew/equipment: Just after Piper freezes the security guard after she and Prue enter the prison, they are walking along a corridor and the shadow of a boom mic can be seen in the top left quadrant of the screen.
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.