The New Adventures of Huckleberry Finn (1968)

Seeking shelter from wolves in a nearby forest, Becky, Tom, and Huck are invited into a scientist's house where his hospitality turns into his own personal science project as he demonstrates his latest invention to them. It's a miniturization machine which he successfully used on a dog. But to prove its full potential, he needs a human subject. Huck becomes his unfortunate victim and in front of the others, is shrunken down to a mere 10 centimeters (4 inches). It's up to Tom, Becky, and the dog to get Huck back to normal size. But will another one of the scientist's experiments lead to their doom?