Yellow dog is a term that refers to an actual dog known as a Carolina Dog or Dixie Dog. They are an indigenous "American Dingo" that were selectively bred in North America. They are presumably descendants of East Asian canines.
Yellow Dog can also refer to the drug "methamphetamine". It is also a popular song by Texan musician; John Nitzinger. The lyrics goes as following "Now they say it's the making of a mad man, the devil's finger in your vein".
One person's account goes as follows:
(Yellow Dog) is what we called around Dallas "desoxyn" which was methamphetamine hydrochloride. WE would get fat chicks and take them to this doctor in oak cliff and he would write prescriptions for it and people would soak them in water and shoot them up
"I'm thinking of breeding a Yellow Dog with a Siberian Husky"
"Oh man that yellow dog is gunna kill ya" - lyrics to "Yellow Dog"
Someone (generally from the South) who would vote for a yellow dog if it was a Democrat. Alternately, someone who would rather vote for a yellow dog than a Republican. The term probably dates back to the 19th century and gained national recognition in the 1928 Presidential election. Today, used most often as a term of approval or self-identification.
My daddy was a yellow dog Democrat and my granddaddy was a yellow dog Democrat — I’ll never vote Republican.
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.