Forky Can Explain Toy Story 1 Sid Mystery
In the original Toy Story movie, Sid's toys couldn't talk -- but Forky, who closely resembles Sid's creation, could explain why they never did.

Back in Toy Story, Woody and Buzz meet Sid's scary-looking toys that don't talk like the rest of the movie—but the ones that appeared in Toy Story 4 Fauci can explain why this is the case. Forky isn't technically a toy, but some modified plastic utensils, leading Forky to call itself "junk". Bonnie, the kid who ends up making the fork at school, thinks the fork is a toy. Her love and affection for Forky seems to give him sentience, allowing him to express his thoughts and emotions, as he is considered a toy for his master.
This is inspired by Sid's toys in Toy Story, as the opposite seems to be true here as well. Bonnie cherishes Forky even though he's not a "proper" toy, and Sid destroys his toys and puts them together in random ways. Since he sees toys as destructive objects, this erases their perception instead of embracing it, which may mean that they are now technically no longer considered real toys due to his perception - the process Could cause them to lose their ability to speak the same way Forky gained it.
How Forky Came To Life In Toy Story 4

Forky's creation story is likely to play out multiple times in real life - unless the creation is revived. In an episode of Toy Story 4, Woody goes to school with Bonnie to make sure she has a good first day. When school craft time came around, Woody would collect the scraps and put them in front of Bonnie so she would have something to use for crafts. Bonnie eventually created Forky on the spot, but he wasn't revived until he was in the backpack with Woody.
When Woody introduces Forky to the family gang, she says, "She really made a new friend", suggesting that Bonnie brings Forky to life, although he's made of trash, unlike the series' List of other toys. The new Toy Story 4 character was confused and intimidating at first, but over time, as Fauci realized how much he meant to Bonnie, he began to understand what it meant to be a toy. Bonnie's love for Forky allows him to talk and feel things.
If Kids Give Toys Life, They Can Take It Too

When kids like Andy and Bonnie can bring toys to life, it means A kid like Sid can take that life away. While Sid's toys in Toy Story are still technically alive, they are unable to express their thoughts and feelings - which makes sense, since Sid still sees them as creations rather than personalities - This is different from how most children describe toys. At first, the toys are scary because they can't talk at all, but Woody and Buzz's new relationship allows the two to work with them to stop Sid from harassing the toys again.
Sid's Mute Toys Can Explain Why Bullseye Doesn't Talk Too

In Toy Story 2, Bullseye joins Woody and other Toy Story characters, as well as Jessie and Stinky Pete. Of the three, Bullseye is the only one who never speaks, and there is never any indication that he does. Sid's toys are muted because they are no longer considered toys, so perhaps that explains why the Bullseye only makes horse sounds. There are other animal toys, like Hamm and Slinky, that can talk, so it's not because Bullseye can't talk because he's an animal.
Bullseye is an odd case, however, because even after he became Andy and Bonnie's toy, he still never spoke word. He's definitely been played with in the past two movies and endeared by Andy and Bonnie from Toy Story, so it's baffling to see him not growing up to talk. However, he is able to express his emotions through his facial expressions and the sounds he makes, making him as sentient as a toy. Maybe Bullseye is a rare case where he is able to express himself and is sentient, but he doesn't have the ability to talk -- or maybe it's because Bullseye on the fictional Woody's Roundup show can't talk, and Andy and Bonnie thought the toy bullseye didn't can speak.
Despite being a supporting character in many ways, Forky has played an integral role in fleshing out characters in the series such as Bullseye and Sid's toy. The love Bonnie gave him gave him life, which shows how powerful a child's love can be in the Toy Story movies. It also shows how strong the child's hatred of toys is, as Sid has the opposite effect on his toys, making him truly the villain of Toy Story.