Originally running 150 minutes when premiered in three 50-minute episodes on the Walt Disney television program in the United States, this film was trimmed to 93 minutes for theatrical release in the US and the UK.
In his novel 'The Prince and the Pauper', Mark Twain does not indicate the age of Tom Canty and Prince Edward VI when the story takes place, but historically Edward VI lived from 10/12/1537 to 7/6/1553 and reigned as King of England from 1/28/1547 (when he was 9 years old) until his death (at age 15) due to a terminal illness.
In The Prince and the Pauper (1962) both Prince Edward and the pauper Tom Canty are played by Sean Scully. In scenes where both characters are to appear together, the scenes were often shot twice and mattes (or masks) were used to combine the two film strips into a third composite film strip in a frame-by-frame process using an optical printer. In one film strip, Sean Scully would play Prince Edward and a stand-in would play Tom Canty, while in the other film strip they would reverse their roles. In reverse shots where one of them is seen only from the back, a stand-in can be used and no compositing is necessary, as at 12:48 where the Prince first speaks to Tom at Westminster Palace and Tom is seen from behind. In side-by-side shots where Prince Edward stays on one side of the frame and Tom Canty stays on the other side of the frame, a static matte can be used to cover the side with the stand-in on the first film strip and the reverse of that matte can be used to cover the side with the stand-in on the second film strip and an optical printer can quickly produce the composite film strip. The shot starting at 15:43 where Prince Edward walks around Tom Canty while both of their faces are visible require traveling mattes that change from frame to frame (at 24 frames per second) making the process much more labor intensive. In the shot with the mirror at 16:33, first Sean Scully dressed as a pauper and a stand-in dressed as a prince (for whom this is a reverse shot) are filmed standing in front of a "mirror" that is a blue or green screen (to make masking easier), then Sean Scully must be filmed two more times for the reflections, once dressed as a pauper, duplicating his movements from the first film strip, and once dressed as a prince, duplicating the movements of his stand-in from the first film strip, then the second and third film strips must be composited into a fourth film strip for the mirror reflection, and finally this fourth film strip must be composited with the first film strip. Notice in the mirror scene that the movements of neither reflection is well coordinated with the movements in front of the mirror. When the boy dressed as a prince approaches the mirror, he takes one last step forward on his left foot causing him to sway left, but his reflection stays perfectly steady. When Sean Scully dressed as a pauper says "I swear to you, no one will know the difference", his head bobs up and down as he says "you" but his reflection is slow to bob.