Other mistake: When Jessie pops the tire on the RV, Bonnie's dad gets upset and says "I just bought it." Throughout the rest of the film however, he says the RV is a rental.
Continuity mistake: At the beginning while Woody is in the closet the letters on his boot disappear.
Suggested correction: The letters are on the other boot that we cannot see.
Continuity mistake: At the beginning, when Andy gives Woody to Bonnie, their interaction and how Bonnie reacts is quite different than the previous film. At the end of Toy Story 3, when Bonnie sees Woody still inside the box she says "My cowboy!," then Andy describes in detail why Woody is so special and gently hands the toy over to Bonnie, and she quietly hugs Woody. In this movie Andy is holding Woody when Bonnie says, "My cowboy!," then Andy gives the toy to Bonnie and she hugs Woody. (00:06:20)
Suggested correction: This may not be a valid correction, but that scene was really just a summary of how it went, kind of like a backstory or a memory. In a backstory events do not have to play out exactly how and when they were, just mainly the important things that happened.
They could easily show correctly how it happened without harming the story in any way.
Continuity mistake: When Andy's house is shown in the previous films the driveway is on the opposite side than it is in this film.
Suggested correction: The original driveway that leads into the garage is still there. They added a second driveway on the left side. (under Molly's window).
Suggested correction: Not exactly a mistake considering he bought a rental.
That's a self-contradicting statement. Buying something means you have ownership of it. Renting something means you pay for its use with the understanding that it will be returned at a specified time. You can't buy a rental any more than you can rent something you buy.
Phaneron ★
Suggested correction: At best it's a character mistake. As he was exasperated as Bonnie's mother says to her "Daddy's going to use some words" apparently meaning he was going to swear.
Joey221995
If it's a character mistake, it's still a mistake, so no correction is needed. I think it's a valid other mistake because it's the screen writers flipping back between owning and renting, but not an actual plot hole. I've been exasperated with a rental before and never in my anger or frustration said I bought the rented item.
Bishop73