Li'l Sneezer's mentor and predecessor is the mouse Sniffles who appeared in several shorts in the 1930s and 40s, though some fans believe that his mentor was Speedy Gonzales, a more well known Looney Tunes mouse.
Sneezer has hurricane-force sneezes and seems to be allergic to many things. He is very hyper and likes to talk a lot, the latter being similar to Sniffles' later appearances. He also addresses everyone older than him as an adult, therefore, he only refers to the other characters as "Ma'am" or "Mister", except in the episode 'The Acme Bowl', where Sneezer is a huge fan of the Acme Looniversity's football team, mainly Plucky, who he calls by name.
Li'l Sneezer is often hunted by Furrball, but his sneezes are so powerful that they prevent the unlucky cat from eating him. Even though Furrball has actually succeeded in putting Li'l Sneezer in his stomach, he was unable to keep him down as Sneezer sneezed his way back out at Furrball's utter dismay (Sneezer states that he is allergic to cats the most). Elmyra has tried to keep Li'l Sneezer as one of her pets, but his sneezes were too powerful for even Elmyra to handle.