In traditional filmmaking, a film crew shoots and shoots and shoots and pulls all the footage into an editing room to see what they got at the end. For animated films, most of the real creative editing happens first.
The Story department hands off their hundreds of individual drawings and editors plop in temp musical score, sound effects, and temp "scratch" voiceover from our talented crew. (We have auditions and everything - if you're cast, congratulations: you are destined to be replaced by big Hollywood stars and comedians!)
The director uses these early cuts to shape the sequences - working out the mood of each scene and the type of performances the voices need to embody - trying out ideas here helps with the final casting and lets everyone at the studio understand how the final scene will play.
Once the actual real casting is done, the Editorial department manages recording sessions with the cast and Directors, eventually inserting the real deal over our temporary dialogue and getting the new cut out to everyone on the production floor.
The Editors are working on the cut throughout the full life cycle of a film, continually working with Story, Camera & Staging, and Animation to make multiple versions of shots and sequences for review and approval - updating the cut with new writing, story changes, cameras, and animation daily during the process.