When you see deleted scenes from animated films, they're often half finished, or don't even have complete voice acting, because they get scrapped early on. However, one scene in Finding Dory was actually completed, before it was decided it wasn't necessary. Director Andrew Stanton says that there was one scene that he thought the film needed, though it was eventually decided to be redundant Check it out below.
aqwhatever she said in her sleep. And then she'd have a flood of memories. My editor Axel Geddes realized it was redundant. You don't need [my] middle step. She can just have that first traumatic experience of being sucked into the rays and in that moment mumble the phrase.

You might recognize the scene's description as it was actually used in early teasers for Finding Dory. However, it wasn't actually used in the final cut of the film. Andrew Stanton explains all this on the newly released Blu-Ray for Dory. Instead, Dory remembers her family while taking Nemo to school and visiting a migration of stingrays. The scene of her having trouble sleeping is nowhere to be found in the final cut of the film.

In live action films, it's not uncommon for scenes to be cut. Once you've gone to the expense of hiring a crew and a cast and you're set up at a location, shooting extra footage you might not end up using costs you next to nothing. In animation, however, it's very different. Everything you create takes extra time and money that could be spent on other things. As such, animation is usually much more efficient. Ideas that aren't used rarely make it past the storyboard process. As Andrew Stanton says, it's rare for a scene like this to have so much work put into it.

Sometimes you stay stupid for much longer than you want to on a film. And on this case, it was almost for four years. This sequence is completely finished, it's lit, it's animated, it's scored. That rarely happens. We usually catch these things early. But we got that far along and realized we had too many steps in Dory's equation to remember her parents... This was a really tough sequence to cut because so many people---an entire orchestra---worked on this you can still see the guilt in my face. It even made it into the first teaser trailer.