According to Diabolique, "the movie kicked off a whole bunch of comedies with a slight fantastical element that powered Disney film division for the next two decades. Much of the credit went to MacMurray; a lot of the credit should have gone to Kirk, whose easy-going boy next door charm made him the ideal American teen."
The words Wilby Daniels recited from the Borgia ring to transform himself were in Latin "in canis corpore transmuto" translated as "into dog body transforms."
The story of Wilby Daniels having to conceal his real self has often been viewed as ironic considering the closeted life Tommy Kirk was leading.