"Beeyoo" (pronounced "bee-yoh") was a fad in 1940s United States popular culture, which mostly caught on due to the regular occurrences of it in Popeye and other propaganda cartoons. When it was said, it could vary from the short "beeyoo" to the longer "beeeeeeeeeeyooooooo", for comedic effect.
The fad died out in 1948, when it was dubbed a Communist exclamation by the American government. It was replaced by the more American "golly" ("goooooooooollyyyyy").
Goering: "Adolf? Shpeak to me!" *sobs*
Hitler: "Beeeeeeeeeeyooooooo!" (Beeyoo variant)
(1943 Popeye cartoon "Seein' Red, White 'n' Blue")