Jake Has This Theory

. . . that everyone develops a default whistling tune. His is the theme from the Andy Griffith Show. Will's is The Girl From Ipanema. I have one too, but I'm not sure what it's from. (I have this sneaking feeling it's a theme from a really early Disney movie, like Lady and the Tramp or something, but that's unverified as yet.) Anyhow, it's making me curious now. Are the Armstrong bros and I just being weird again, or is this a real phenomenon?