Other mistake: When Piper and Mark are in the police parking lot she holds the door open for him to get into her SUV. When he gets in you can see the SUV go down from his weight in the vehicle. Ghosts are supposed to be weightless.
Charmed (1998)
1 other mistake in Dead Man Dating
Plot hole: When Gith takes the potion from Chris, he ends up stomping on it and shattering the potion bottle - making contact with the potion. We've seen that potions don't have to be thrown by someone who's even a witch for them to work (like when Cole's powers were stripped etc) so why on earth would he do this? And how did it not vanquish him? There are other ways he could have gotten rid of the potion that didn't involve a way that really should have vanquished him.
Cole: Phoebe, I love you. I don't know what's going on but maybe I can help. Would you like me to kill someone for you?
Trivia: Holly Marie Combs's real life pregnancy with her son Finley Arthur Donoho was mirrored by Piper's pregnancy with Chris in this season.
More questions & answers from Charmed
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.