Other mistake: Approximately four minutes into the episode, two demons go to the manor. Pru catches them and "throws" them to the one side. Her arm motion would fling them to the right, but they fly to the left. (00:04:15)
Sleuthing With the Enemy - S3-E8
Other mistake: When Piper puts the Belthazor flesh into the Belthazor vanquishing potion, she is the only one that gets "blasted" back even though she is the one standing farthest away from the stove and the potion.
Sleuthing With the Enemy - S3-E8
Other mistake: Cole is supposed to be one of the most powerful demons alive, but a small cut from Piper weakens him to the point where he can't even shimmer or keep up his "Cole" appearance.
Coyote Piper - S3-E9
Other mistake: At the beginning of this episode, Tara and Kierken are arguing and Kierken says that he could always "suck you into your little mixing bottle and start again." Then Tara says that "she has a better idea," and then she stabs herself. The life essence automatically flows out of her but the knife was still in her body. Later, the possessed business man stabs himself in front of Piper and she kneels down to see if he was okay and the essence flew into her, without the knife being removed from his body. At the end, when Leo comes down after Prue stabs the possessed Piper, he kneels over her, but the essence does not flow into him. It only flows into him after he takes the knife out of her body.
Pre-Witched - S3-E17
Other mistake: During a flash back of Grams in the kitchen she puts a rose in a pot, then Piper walks in, they talk and Piper starts to add some salt and a couple other ingredients into the pot. Grams asks how she knows what to add, Piper says says something about mustard - Piper wouldn't know what's in it already, she just walked in. And she never even finds it strange that there's a rose with a stem in it.
Other mistake: At the start of the episode when Prue and Phoebe are walking down the street (just before they find the box), the person with the green jacket on (in the background) reaches into the homeless man's hat and just "scrapes" the bottom of it. Not putting any money in, or taking any money out - a completely pointless action. (00:02:05)
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.