Clench and Puzzlevision are the same person.
(Still needs images)
This is because Clench is Tari's robotic arm. And what do we know about Puzzlevision? He has control over any and all technology that he wants. We know this by the fact that during 'It's Gotta Be Perfect' he was able to control and infect SMG4 by advertising the keyboard that 'would make his work perfect' on his computer and also came up when 4 had finished asking if he wanted to review the keyboard; in 'Western Spaghetti' he used the TV to lure Meggy in by showing her an advert of One-Shot Wren, her idol at the time, being at Western Spaghetti; and in 'WOTFI 2023' printed out an image of SMG3's notebook for Marty to see so that he would lock onto that, and at the end was in a room that looked like it had things in it to control all sorts of technology through a single TV.
Clench also knows where Tari came from, which is something that we and the rest of the SMG4 Crew don't know, and was able to recognise her as her easily and quickly, which proves that he knows a lot about her and who she is, which Puzzlevision would know as he's been watching and keeping an eye on the SMG4 Crew ever since 'It's Gotta Be Perfect' and maybe even longer than that.
Clench is also in scenes where Puzzlevision isn't; for example, in 'SMG4: No TV Make Mario No Okie Dokie' when the TV dies, Clench dies afterwards, but then soon comes back online when it's just him, Tari, and Meggy, yet turns off again when the main crew, and Bob, are about to go down into the basement, where Puzzlevision is. This means that Puzzlevision would be able to constantly keep an eye on the SMG4 Crew at all times, which is exactly what he wants, and would also have a new and close perspective on everyone. And I think that the reason he helps Tari is in order to 'blend in' with the rest of the cast so that he doesn't arouse any suspicion from anyone.
On top of that, he hid himself when SMG4, SMG3, and Bob were chased into the same room as him, Tari, and Meggy by Mario in 'SMG4: No TV Make Mario No Okie Dokie', but why? In 'SMG4: The Day My Arm Went Physco', Clench didn't have a problem with who saw him and was very extroverted and didn't stay hidden, so why suddenly now? I think that the reason why is that he hid himself from SMG4. Why? Because SMG4 is the only one who has been directly under Puzzlevision's influence and control in the main gang during 'It's Gotta Be Perfect', he would be able to put two and two together and figure out that Clench is not their friend, isn't on their side, but is in fact Puzzlevision in disguise.
He was also introduced only an episode or two directly before the lore started up again; Luke and the team would not put in a character for no reason!