The fox in the Pinocchio movie sings "Hi diddle dee day, an actor's life is gay".
I find in the dictionary that the word "diddle" means "to cheat or swindle", but when used in combination with "dee", does the word "diddle" still carry such a meaning?
On page 156: Pinocchio will not follow the advice given by his conscience in the previous song (126.96.36.199 “Give a Little Whistle”) and the next song, “Hi-Diddle-Dee-Dee”, proves it. The wooden boy has just been given a conscience but he is taken by a cunning fox and a bad cat, which symbolise temptation and evil, along the wide easy path of fame. It is curious the way they cheerfully sing when they are leading Pinocchio away from his conscience. The repetition of the anaphora “Hi-diddle-dee-dee”, rhythmically accompanying the singers on their way, is a poetic device of sound and at the same time represents the way the singers of this song move rapidly up and down or backward and forward. This is what diddle means …
You also find "diddle" in the Mother Goose rhyme Hey, Diddle, Diddle, the first three lines of the six being: Hey diddle diddle,
The cat and the fiddle,
The cow jumped over the moon.
The rest is on that Wikipedia link.