Lummie

Continuity mistake: When the dentist wants to put Nemo in a bag, it's a resealable one with a seam at the top. When he finally catches him, it has changed to a normal plastic bag.

Dr Wilson

Factual error: At the end of the movie it shows all of the aquarium fish in the ocean inside of their bags. It also shows the bags almost completely out of the water with only a small portion under water while the bags are almost completely filled with water. With this amount of water the bags should be submerged underwater with only the little amount of air showing on the surface, because water is not lighter than water; water weighs the same. (01:32:40)

Deliberate mistake: When Dory is inside the whale, she doesn't have the scars from the jellyfish sting anymore. [This is actually a long-standing Disney tradition. The company seems to believe that it is less traumatic to see violence onscreen if the evidence is gone immediately (blood, scars, etc. always disappear). Still an error, but it wasn't the fault of the CGI animators.] (01:09:30)

Continuity mistake: The "'For a bite that counts', alligator floss'" poster on the wall moves further from the window as Phillip Sherman grabs Nigel, then it suddenly moves back to its original position. The poster is first visible close to the window in an earlier shot. (01:19:50)

Trivia: In the waiting room of the dentist's office you can see a Buzz Lightyear action figure lying on the floor. (00:25:35)