hog heaven

The idiom "happy as a pig in mud" is closely related to the concept of hog heaven. It shares the idea of pigs being in a state of extreme happiness and contentment. Pigs are known to enjoy rolling in mud, which not only helps them cool off but also protects their skin from the sun and insects. When pigs are given the opportunity to engage in this behavior, they are often seen with big smiles on their faces, fully enjoying the experience.

Similarly, being "high on the hog" is another expression related to hog heaven. This phrase originated from the fact that the best cuts of meat come from the upper portion of a hog, which is considered to be of higher quality. Therefore, someone who is "high on the hog" is metaphorically enjoying the best things in life and living in a state of luxury and indulgence.

On the other hand, the idiom "happy as a pig in shit" is a more vulgar variation of "happy as a pig in mud." While the original idiom emphasizes the pig's happiness and contentment in a less explicit manner, this variation uses a more crude phrase to convey the same idea. However, due to its colorful language, it is considered more informal and would not be appropriate for all contexts.

While these idioms share the common theme of happiness and contentment, they each have their unique nuances and levels of formality. Hog heaven is a more general expression that can be used in a wide range of situations, while "happy as a pig in mud" and "happy as a pig in shit" add specific imagery and tones to the description of extreme happiness.