Scratchy is a cartoon cat from the show Itchy & Scratchy, an obvious parody of Tom and Jerry. His enemy is Itchy, a blue mouse. In almost every episode, Scratchy is brutally hurt and sometimes killed by Itchy. There are only three episodes in which Scratchy is not hurt, the episode in which Poochie debuts on the show, Dogday Hellody of 1933 the one where a jury of Scratchys finds a dog on a trial guilty and the only episode in which Itchy is hurt by Scratchy.
He is a parody of the character Tom from Tom and Jerry. Itchy and Scratchy fight with each other in more violent ways as to how Tom and Jerry do.
The Itchy & Scratchy Land is an Itchy and Scratchy theme park. It has parades with robots resembling Itchy and Scratchy which are supposed to be inoffensive and only attack themselves. While on vacation, the Simpsons were attacked by a group of robots, until they used the cameras flashes to short circuit them (the reason flash snaps are not allowed).
In "Treehouse of Horror IX", Scratchy finds a love interest in Snowball II. (The Simpsons' family cat)
For a full list of both Scratchy and Itchy appearances, please see The Itchy & Scratchy Show