Sewernose de Bergerac is a semi-anthropomorphic alligator with an infatuation for theater. He lives in the sewers under the theater.
Sewernose is an alligator with bushy brown eyebrows and yellow eyes with crazed looking two-colored irises (red and green), usually clad in a short red and black cape and a purple cap with a green feather.
According to Sewernose himself, he was flushed down a toilet when he was still young. He then lived in the sewers just under the theater, where he learned to appreciate the opera and learned from the best actors and singers who performed there.
His love for theater greatly shows in his personality. He loves dramatic entrances, vanishes with a puff of smoke and has his very own puppet show. He thinks of himself as being a great actor and dreams about a starring role in an opera.
Most of the time, he is "accompanied" by Euripides and Voltaire, both of them having their "own" unique personalities.
He seems to have some sort of multiple personality disorder, thinking that Euripides and Voltaire really are alive (a fact which becomes vital to the plot later in his episode).
The Rangers caught sight of him (or rather his puppets) when he tried to put Clarence Dudley, the lead actor in a local play, out of action so he could later take over his part. He failed, and the Rangers followed him into the sewers.
While the Rangers were investigating, Sewernose caught them, and proceeded entertained himself with his puppet show, using the Rangers as marionettes. Later, he tried to get hold of Clarence Dudley again. Succeeding this time, he put on Clarence's costume and entered the stage, but when both the cast and the audience realized that the star was an alligator, they tried to flee in panic. Outraged by all these "critics", Sewernose threatened to eat them all. He could only be calmed down by Chip and Dale taking over parts in the opera, causing Sewernose to start acting again.
He was later flushed back into the sewers.
Behind the scenes
Sewernose de Bergerac appeared in a single episode, namely A Case of Stage Blight.
As mentioned by Tad Stones, Sewernose was loosely based on the comics-only character Sewer Al.