At one point, Piper is holding the baby by supporting his weight with her right arm. The camera then cuts to another angle, and she is now supporting him with her left arm.
When Prue is shopping for baby items at what seems a local drug store, they show Kirkland branded diapers, which are only sold at Costco warehouses.
When Prue supposedly bought diapers that are the wrong size, it is obvious that the side of the diaper is folded in to make it look like it won't fit.
When Prue and Piper are changing the baby's diaper and the camera shows only the baby's foot at the bottom of the screen, it is obviously a doll's foot.
At one point the baby is crying and his mouth isn't open.
Right after Prue gives the baby a bath, he starts crying after she puts him down and Piper freezes him. Just as she's doing that, the baby actor turns his head to look at her and he is not actually crying.