The wild season 1 finale of Chucky introduced a major plot hole involving Junior joining Chucky's side. Going into Chucky's TV debut, many veterans of the Child's Play movie series wondered if cinema's most iconic killer doll would work on TV. That's especially due to it airing on basic cable, which many thought would lead to a toned-down final product. Thankfully, Syfy and USA didn't hold Chucky back, allowing the show to include lots of gory kills and foul language. The only slasher area the Chucky show lacked in was sexual content, but considering most of the main cast were teenagers, that's for the best.
Overseen in all creative aspects by original Child's Play creator Don Mancini, Chucky season 1 was clearly made for fans first and foremost, with mountains of references to the past and lots of legacy characters. Some could even argue there was the potential for those unacquainted with the Child's Play movies to get lost as to what exactly what going on and why certain characters were important. For those who already loved Chucky though, this wasn't a problem. One of the most interesting new characters Chucky introduced was Junior Wheeler (Teo Briones), cousin to protagonist Jake Wheeler.
Junior began Chucky as a pretty meek person, getting pushed around by his girlfriend Lexy, and used as a vicarious vessel for his dad Logan's athletic dreams. However, by the end of Chucky season 1 Junior had completed a transformation, becoming the killer doll's new protege, and even using the doll itself to murder his father. Where the plot hole comes in is that Chucky used Tiffany - in Jennifer Tilly's body - to convince Junior that his dad had been having an affair prior to his mom's death. Yet, when Junior goes to Chucky's house, he has zero reaction to seeing Tiffany, which makes absolutely no sense.
While Junior was clearly on edge around his father from Chucky's premiere, it was this alleged affair between Logan and Tiffany that truly pushed Junior over the edge into patricide. Chucky even harps on it in the moments directly before Logan's murder. If Junior hadn't thought his dad was cheating on his deceased mom, it seems unlikely he'd have grown angry enough at him that murder was the result, thwarting Chucky's grand plan to build an army. Yet, when Junior sees the woman he believed his father was having an affair with at Chucky's home, there's no realization. Seeing her there should've really been used to explain the moment later where Junior turned on Chucky and helped Lexy, as realizing he'd been manipulated into killing his own father would've given Junior more reason to switch sides again.
The fact that Junior doesn't seem to notice his father's supposed lover hanging out with Chucky is even more inexplicable because he had a face-to-face conversation with Tiffany in Chucky episode 7. It's not like he'd only seen Tiffany from a distance at his mother's wake; he'd stood mere inches from her face, and spoken to her directly. As tightly written as so much of Chucky was, the idea that this kind of mistake didn't get noticed somewhere during production is downright baffling. With Junior now dead, the damage is mitigated somewhat, but the plot hole definitely remains.