Continuity mistake: When the Charmed Ones' father, Victor, came to San Francisco in episode 1-3: "Thank You for Not Morphing," his last name was Halliwell. But when he came back in the third season and later, his last name was Bennett.
Magic Hour - S3-E2
Continuity mistake: In this episode, Phoebe says "Grams, you were married four times." But in "Lost and Bound," Phoebe tells Cole that Grams was married six times.
Continuity mistake: When Prue was talking with the shut-in and the security guard comes up and knocks on the door you can see the the chain is on the door. When he knocks again and says he is coming in and tries to open the door the chain is off.
Continuity mistake: The timeline in the episode is inconsistent. Right after the first courtroom scene, we see the three sisters at home, and Phoebe says that "Cole was an angel in that courtroom yesterday." Later, Cole says that he regrets the criminal being let go, "today." But they are talking about the same events.
Continuity mistake: When Cole catches Phoebe's karate kick at her school, her foot is up near Cole's shoulder, but then moves down much lower. (00:18:20)
Continuity mistake: When Prue talks to Piper after stopping her phone conversation, she tells her that "the Sin Balls work a lot faster than [they] thought. Once infected, the victim only has a few hours before it drives them to total self-destruction." However, this is almost verbatim what was written in the Book of Shadows. It could be easily read by the viewing audience when the book entry was shown. So all three sisters should already know this.
Continuity mistake: When Kate was drawing the trolls in one shot she had a peach coloured crayon, and in the next shot she had a purple crayon.
Continuity mistake: Piper says she wants to go to Paris by plane not by orbing, but in the episode "From Fear to Eternity" flying was Piper's greatest fear.
All Hell Breaks Loose - S3-E22
Continuity mistake: When they first bring the doctor to the manor the sisters tell him they're not sure who's trying to kill him, then a few minutes later Prue tells him exactly whose trying to kill him, Shax, the Source's assassin.
Continuity mistake: When Cole gives Phoebe his card on the school campus, it disappears and reappears between shots. (00:23:25)
Power Outage - S3-E7
Continuity mistake: During the training drill, Piper fumbles for a knife on a table in front of her. In the shot of the table, she loses hold of the knife as she pulls her hand up, but when we cut to a long shot, it is back in her hand.
Magic Hour - S3-E2
Continuity mistake: When Piper and Prue are talking to Brooke outside, Piper's arms change from being crossed to having her hands on her hips between shots.
Continuity mistake: When the trolls attacked Piper outside P3, her bag got flung into the shadows, but in the next shot, her bag was right next to her, and in the light.
The Good, the Bad and the Cursed - S3-E14
Continuity mistake: When Cole and Prue are about to shimmer to the other plain to find BO, Cole's face has not been shaved. But when they reach the other plain, his face is cleanshaven.
Continuity mistake: When Prue telekinetically moves the sin ball box across the street she moves it ALL the way across but when the man infected with greed goes to get the box, the box is only halfway across the street.
Pre-Witched - S3-E17
Continuity mistake: When Piper is sitting with Leo on the tailgate of the SUV, when shown from the front her hair is in front of her shoulder and ear, but from the back we see it tucked behind her ear. This switches constantly throughout the scene.
Continuity mistake: When Prue and Piper leave to help the hostage, Piper asks Leo, "Do you think she's mad?" Her hair is in front of her shoulders. Immediately afterwards, she sits on the couch with Leo. Her hair is behind her shoulders.
Continuity mistake: During the scene where Piper is ordering merchandise from Bloomingdale's and Prue, she and Phoebe realize the "sin balls" infected them. Piper's hair constantly changes from being in front of her shoulders and behind them.
We All Scream for Ice Cream - S3-E10
Continuity mistake: When the girls are saying goodbye to their father, Phoebe hugs him around the neck, then lowers her arms while they talk. When her father says "About anything," her left arm jumps back up to being around his neck, and in the next shot, it's down at the side again. (00:40:20)
Continuity mistake: When Prue is in the basement with the priest she has curly hair, but when she comes upstairs to vanquish Vinceres it is completely straight, but she definitely didn't have time to straighten it.
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.