Continuity mistake: When Melinda Dillon breaks the lamp, it is broken into many pieces, but when Darren McGavin is gluing it back together it is now in much fewer and bigger broken pieces. Obviously different broken lamps were used.
Continuity mistake: When Scrooge walks into the Cratchit home at the end, there is a "Home Sweet Home" plaque on the wall. The shot then cuts away from it. The next time the plaque is visible, its lettering has changed.
Factual error: In the shot of the start of the race at Agua Caliente - some of the horses in the line up are wearing ring head bridles (an Australian stock horse type bridle) - it would be unlikely that these American horses would be racing in such bridles.
Factual error: Alex is racing his bicycle across a bridge over the Detroit River on the way to the stadium. The bridge is the one leading from the Detroit mainland to Belle Isle, an island park, where there is no residential area.