The thirteen Tom and Jerry shorts made by the Czechoslovakian director Gene Deitch are infamous for their poor quality and rather disturbing nature, featuring badly done sound effects and animation and having a more realistic feel to the violence.
Some have speculated that Deitch didn't like the concept behind Tom and Jerry and was pressured into making them, and wanted to make the people who watched his take on it feel bad for liking the concept. What many people don't know is that Deitch was originally signed on to make more than the thirteen episodes the public has access to. Desperate to get out of his contract, Deitch made one more Tom and Jerry short that few have ever seen.
The short was called "Tom's Basement." It opened with Tom in a typical Tom and Jerry house. His owner was the fat, angry guy from other Deitch shorts. Tom's owner seemed even angrier than in his other appearances; the first scene is him stomping on Tom's tail in a very realistic and painful looking way because Tom is sleeping by the basement door.
The owner yells at Tom to never go down there. Tom is clearly terrified and runs away to another room. Our view stays in the room by the basement door and we see Jerry come out of a mouse hole. He looks truly grotesque, far more off-model than in the other Deitch shorts. He gets an evil look on his face and follows Tom into the next room.
The next few minutes are fairly formulaic. Jerry repeatedly manages to trick Tom into chasing him to the basement door a few times, but each time the owner catches Tom he inflicts a painful looking injury on him, which stay with Tom even after the scene ends. After three beatings, Tom is bruised all over, bleeding in a few places, and limping on a broken leg.
After this, Tom starts to literally beg Jerry not to bother him any more; he's not really talking, but he's crying and mumbling, and you can tell what he's doing by his body language. Jerry just laughs at him and pushes him back to the basement door.
The owner catches Tom again and goes ballistic. The camera zooms in on his face - it changes color and distorts as he yells at Tom in a much louder voice than any other sound in the cartoon. I can't post most of what he said on here, but it's definitely vicious and furious.
It seems like Jerry has finally decided to take pity on Tom, though. Jerry picks up a knife that was lying around and stabs the owner in the leg, quite graphically.
Tom opens the basement door and they carry the owner's body down the stairs. There are dozens of other bodies down there, decaying and showing signs of their violent deaths. Tom and Jerry shake hands and it seems like they've triumphed over the serial killer... But Jerry gets an evil look in his face again and Tom says, in that ghostly, deep voice...
"DON'T YOU BELIEVE IT!"
Jerry stabs Tom, killing him, and throws his body into the pile. The last shot is Jerry putting up a 'For Sale' sign on the yard of the house, laughing, clearly planning to do it all again.
I remember and episode where Tom said "Don't you believe it"....buuuut I don't think Jerry killed Tom and his owner. XD