The Astronomer's glasses disappear and reappear in between shots when he is visited by Mr. Fig.
When Mr. Fig emerges from hiding and tries to snatch the golden globe away from Jimmy but ends up falling into the pond, the little boy clearly does not move fast enough, leading to Mr. Fig to clearly step around Jimmy in order to fall into the pond.
During the climatic foot chase around the World's End maze, Mr. Fig clearly slows down running and falls behind every time when he is just about to catch Jimmy who is running with the golden globe.