Revealing mistake: When Sparky's tail pops off there is a hole where it popped off. But when the tail goes into the bucket the hole is gone.
Continuity mistake: In the scene where Victor's mother is looking at his chalkboard in the attic, Victor's drawing of Sparky has the word "Alive" above it. Later on in the film, when Toshiaki, Edgar, Bob, Nassor and Weird Girl go into the attic, the word "Alive" is missing from above the drawing of Sparky.
Answer: The movie doesn't appear to be set in a particular decade, probably to give it a more timeless appeal. Styles seem to range anywhere from mid-to late-20th century.
raywest