A Hanna-Barbera canine cartoon saying for "Uh-oh," beginning with THE JETSONS' Astro (1962) and continuing with Scooby-Doo in the Seventies.
Astro tended to speak a kind of English except that words with beginning
consonants were replaced with an "R," and "R" was inserted in front of vowels.
Scooby-Doo was less fluent, but was given "Ruh-roh" as a kind of
running gag when things were going bad.
Now "Ruh-roh" is sometimes used as a jocular trope where dogs are concerned, as in a recent news story about a dog who was
accidentally released by Air Canada from his cage at the San Francisco airport. Rough meaning: "I goofed" or "I'm in trouble."