Continuity mistake: When Paige is trying to convince Piper and Phoebe that she needs to save Larry's soul, she has the Book of Shadows open to the page on vampires. In subsequent shots, the open page changes to two different demons; but Paige's hands are down by her sides the entire time, so she couldn't have flipped the pages over. (00:26:35)
Continuity mistake: When Phoebe is walking the Dwarf to the door after finding out Piper pulled the sword from the stone, he steps outside and goes into fast-forward, then stops and goes back to normal speed as he sniffs a flower. During this, in the background, you can see Phoebe, who freezes the whole time. (00:18:40)
Continuity mistake: As Piper is talking to Mordaunt at the Round Table, her fringe changes from in front of her face to behind her ear to in front of her face again.
Continuity mistake: When the sisters first see the lady in the lake, the demon off to the side throws a knife into her back, but the knife hits completely straight, as it would if the demon had been directly behind her.
Continuity mistake: When Phoebe is told that Jason asked not to be disturbed she decides to go in anyway, and right before she enters Jason's office the lace-up on the back of Phoebe's top is very loosely tied so we see a lot of skin, but when she's inside Jason's office the lace-up is tied quite tightly so only a bit of skin is seen. (00:11:40)
Other mistake: Paige's spell causes Darryl to acquire invulnerability and uncontrollable super strength. When he opens the door of the squad car, he accidentally rips it completely off. When he tries to put the suspect into the back seat, the man flies through the car and barrels out the other side, taking the other door with him. But immediately before this, Darryl high-fives several of his fellow officers, and they are unharmed. They should have been thrown off their feet and suffered multiple fractures in their hands.
Continuity mistake: When Paige and Phoebe are knocked over by the large monster, the rug moves itself from being spread across the floor to scrunched up under them between shots.
Plot hole: It's shown with the spell that the Halliwells leave for Chris in the attic that if something happens in the past, the future will immediately reflect that change. Chris had changed so much in the past that there should have been at least one thing different that mildly surprised him, even if he was careful to not give too much information to the sisters about the future.
Continuity mistake: In this episode, Chris thinks back to when he went back to the past. When he and Bianca are on the tour of the manor, there are some costumes that have been worn by the charmed ones. But in the episode "Oh My Goddess (1)" Chris tells Phoebe that Paige died on that day, so how could she have worn something after she died? And if she did die that day, Chris would have never met her, since he was not yet born, and could not have learned to orb from her, as he says in "Spin City." However there are other inconsistencies with that story that Chris mentions later, seeming to suggest he lied about this to get the sisters onside. It may not be a continuity error but as it was never fully addressed in the show just what Chris was lying about (and he obviously told some) we cannot be sure.
Revealing mistake: In Chris's flashbacks, it's supposed to be the day he left to come to the future. But his hair is longer than it was in the season 5 finale when he came to the future.
Continuity mistake: When Chris and Bianca go to the manor to get Chris to go to the past, which would end up him appearing in "oh my goddess"; he's only wearing a black shirt and pants. When he arrives to the past in "oh my goddess" he's wearing a jacket, red shirt, and sunglasses. He wasn't wearing that in Chris-Crossed. And he didn't have time to change to that outfit.
Witchstock - S6-E11
Continuity mistake: When Chris orbs Phoebe from Hong Kong, Phoebe raises her arms to hug Piper twice. (00:00:50)
Witchstock - S6-E11
Plot hole: In the opening scene, Chris directs Piper and Phoebe on how to vanquish the amorphous demon. He says that it will attack "fast and hard" as soon as it senses Phoebe's magic when she levitates. But Chris had orbed out of the warehouse and back in, and the demon didn't react to the magic. Later in the episode, it is specifically attracted to a use of orbing, several times.
Witchstock - S6-E11
Continuity mistake: In this episode, it's 1967 and Grams is young and unrecognizable compared to her older self. But in "That 70's Episode," it's 1975 and she looks just like she does today, not to mention that she has two grandchildren. Grams sure ages quickly...
Witchstock - S6-E11
Plot hole: This episode takes place in 1967, and Penny (Grams) is married to a man named Allen Halliwell who dies in the episode. Allen is supposed to be Penny's "first husband," Patty's father and the Charmed Ones' grandfather. But it was previously established that Patty's father was named Jack, and he died in 1964. Also they hint that Patty is still little but we know she was born in 1950 so she would be 17.
Witchstock - S6-E11
Continuity mistake: Robin falls over backwards after Paige dumps a cannister of marbles onto the floor. But Robin wasn't moving at all when this happened. Trying to walk over marbles will make you fall. Standing still while marbles roll around and bounce off your feet? Not so much.
Witchstock - S6-E11
Character mistake: Phoebe, who has moved to Hong Kong, tells Paige that she, Paige, was born in the Year of the Ox. But Paige was born in 1977, the Year of the Snake. 1973 was the Year of the Ox.
Witchstock - S6-E11
Plot hole: After Paige changes the past, the ghost of Grams changes from a no-nonsense demon-hunter into a pacifist hippie. So, apparently, we are now in an alternate timeline where Grams never became assertive, and stayed a hippie all her life. The episode went to great lengths to establish that if Grams had stayed a hippie, she and the Charmed Ones would have all died young. But the ghost of Grams was still middle-aged, instead of decades younger, and Wyatt and Chris were still there, but they wouldn't have been if their mother Piper had died as a child.
Visible crew/equipment: In the scene with Chris and David in the attic, a boom mic dips into the shot. (00:28:50)
Continuity mistake: When Piper, Paige and Phoebe are having a food fight, Piper freezes the cake, then she throws it at Paige who suddenly has a mysterious stain on her top. Then Piper has orange food on her hands even though she hasn't touched anything orange, and the stain on Paige's top has gone.
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.