Wouldn't Hit a Girl: Jerry is able to cross-dress to fool Tom sometimes, and Tom won't go after him because of this, until Jerry's dress falls down or something.
Would Hurt a Child: Though probably not again after the beating Jerry gave him for hitting Nibbles.
Audience Surrogate: In the sense that she was written to be a bridge between the everyday human world and the insane antics of Tom and Jerry, and is often the only human character present in the shorts she's in.
The Other Darrin: Played straight in the reruns that air in the modern-day. Because of Values Dissonance, Lillian Randolph's voice for Mammy Two Shoes is often redubbed with June Foray's voice (or Thea Vidale's voice); averted in the theatrical version. When Hattie McDaniel (the actress best known for playing the black maid on Gone with the Wind and the inspiration behind the character) died, Mammy Two Shoes was retired and replaced with either a white housewife, a man, or sometimes there'd be no human character.
Nibbles / Tuffy
Big Eater: He has both Tom and Jerry beat in this department, which is quite a feat itself.
Canon Immigrant: Actually debuted in the comics before appearing in any shorts.
Composite Character: When he appears in modern Tom and Jerry adaptations, his name has usually reverted back to Nibbles but he still speaks in a French accent, a nod to the Mouseketeer shorts.
I Have Many Names: Well, only two, and they haven't been used with much consistency. He was Tuffy in the Mouseketeer shorts and some of the later shorts, but in his first appearances and in some of his modern ones he goes by Nibbles.
Spike
Androcles Lion: He protects Jerry in a lot of shorts after Jerry does him a favor.
Brown Bag Mask: When concerned that he's ugly in Downhearted Duckling.
Driven to Suicide: In Downhearted Duckling, where just because he thinks he's ugly, he attempts to cut himself in half with an axe, and later tries to force Tom to eat him (and Tom is more than willing to oblige before Jerry stops him).