Factual error: Throughout season 8 the members of the Triad wore a pentagrams on their gowns that would alternate from the point being up and point being down. They should only be wearing a pentagram with the point facing down. Pentagrams with the point facing up is the symbol for practitioners of white (good) magic while those who practice black (evil) magic is symbolized by the point facing down.
Continuity mistake: In this episode, the sisters go back in time to late March 1975. On the family tree it says that Piper was born on August 7, 1973. So she would be 1 and 1/2 in March 1975. But she looks at least 2 years too old. (00:09:30)
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)
Continuity mistake: After the "dirtbag" is brought back to the manor and Piper is ragging on him, Piper gets very angry and decides to blow her husband up. Less than a minute later, Cole says "Back away slowly, Leo." Leo says "What?" and Cole says "She's becoming a fury." Then it shows Pipers hands, which now have long black fingernails, but they just suddenly show themselves right when Cole decides to show up and say she's becoming a Fury. When she blew Leo into orbs there were no long black nails. (00:25:35)
Factual error: In the opening scene in Salem, Melinda Warren is going to be burned at the stake. But in the real Salem trials, no one was burned; all of the people convicted of witchcraft were hanged.
Wrestling with Demons - S3-E12
Continuity mistake: When Rasputin first lay on the couch, he was at the end of it, but two shots later he was suddenly in the middle of the couch.
Revealing mistake: When Phoebe punches Dr. Williamson, it's easy to tell that she doesn't really punch him.
Revealing mistake: The sheet-covered body of Charlene that is being moved by the police has obviously got a head, despite the fact that she was meant to have been decapitated.
Revealing mistake: When Maggie Murphy climbs onto the ledge of the roof to jump off you can see the surface of the ledge dipping as if it was foam.
From Fear to Eternity - S1-E13
Plot hole: Prue finds an entry in the book of shadows about the fear demon written by her mother. How would her mother know anything about this demon when no one has seen him in nearly 1300 years, let alone how to defeat him?
Continuity mistake: In this episode, the Cupid needs his ring in able to "fade" from place to place but in Season Eight Coop loses his ring to a demon and he is still able to "fade" from place to place. (00:18:00)
Love Hurts - S1-E21
Continuity mistake: In this episode Leo specifically tells Prue, Piper and Phoebe not to touch the Darklighters arrow because it is poisonous however in future episodes/seasons, the Darklighter arrows are only poisonous to Whitelighters. (00:06:30)
Continuity mistake: When Chris's hand gets stuck to the first aid kit, the position of his hand changes between shots.
Other mistake: When Andy, Phoebe and Prue are in the attic figuring out how to vanquish the ghost of Alcatraz, pages starts flipping, the book opens up to the page where the truth spell is, and Andy finds out that Prue cast that spell on him. Later when he asks how much time Prue gave him to react, she says "a minute or two". But in the episode "Truth is out there" (1-8) it was first in Prue's office when she told him, and the clock on the wall shows that it's 25 past 5. And it was 8 o'clock when Prue cast that spell. So few hours later when Andy and Prue are at Andy's door, it's almost 8 o'clock and Prue says she needs the answer now. So doesn't Andy have more like few hours rather than few minutes to react?
Continuity mistake: Leo says that Piper's past lover is his past life. If it was a past life, in 1924, that means Leo must have died almost straight away to be old enough to qualify as a doctor in WW2. And it wouldn't be his past life but his own past if it was the same life from before he became a Whitelighter. But then he'd also have been 15-20 years older before he died in WW2.
Continuity mistake: In the church scene when Phoebe and Piper are showing Paige how to use her power, Piper says "according to the prophecy, the third sister has the power to move things with her mind, like Prue could." Prue was not the third sister, but the first. Paige is technically The Fourth Sister, but since the prophecy didn't speak of a "Power of Four", she would automatically become the third sister after Prue's death. (01:02:42)
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.