Continuity mistake: The letters A and B on the bottom row on the blackboard differ styles between shots, being wobblier in the second shot.
Continuity mistake: When Merlin searches for the model plane the knot holding it swaps from neat to crappy between shots. (00:56:02)
Continuity mistake: When Ector and Kay fight, the mallet behind turns 180ยบ. (00:49:30)
Continuity mistake: Before Kay cuts the mop's handle, the mop is dark brown. After he cuts it turns to vanilla coloured.
Continuity mistake: When Merlin arrives from the future, he talks about it to Arthur and puts the crown on his head. The sword, resting against the throne, appears and disappears randomly all the time.
Answer: Arthur was voiced by three actors. Rickie Sorenson and Richard and Robert Reitherman. Rickie originally voiced Arthur but, during production of the film, Rickie hit puberty causing his voice to change, so Wolfgang Reitherman chose to use his own sons to replace Rickie.