Mucus is the villainous mascot for the Mucinex brand of decongestion medicines He wanted a place to call home out of the insides of his human hosts, but is quickly evicted with the proper dose of mucinex.
Surprisingly the character has gone through many changes since his first appearance. In his earlier appearances he was portrayed as single squatter who stubbornly refuses to leave a persons lungs until they took Mucinex. He was then shoved away by a large box of Mucinex only to return inside someone else and made different attempts to make sure he couldn't be moved, including attempting to duck tape himself down. Once, he took the form a giant western outlaw only to be quite literally blown away by sheriff Mucinex. Later he became married and had a son named Junior (used to advertise children's Mucinex). It is also revealed that he has an enormous extended family, all of them equally as stubborn. In his last appearance to date he has a new friend called "The nasal sweller" who resembles a bouncer but he too is defeated by Mucinex.
The new Mucus
Recently, A new Mucus has appeared with a drastic new look and a new voice. This new mucus has a more updated personality and attire and is seemingly more of an annoying jerk than a squatter. One major difference is that, unlike the first Mucus, humans are fully aware of his presence and he exists in the world. People are usually seen trying to get rid of him as he won't leave them alone. In his ads so far, he tries to convince a woman not to use Mucinex, blurts out spoilers in a crowded movie theater, and tries to join a man for work (without permission) for "taco Tuesday".