Crosswise is one of the 101 Dalmatians at the Dearly Farm.
He was the only puppy in his old home and hasn't adjusted well to being one out of ninety-nine. This is made worse by the fact that no one can remember his name correctly.
His recollections of his younger puppy years are a bit distorted. While he remembers his biological parents fondly, they were actually strict, mean, and verbally abusive. Crosswise was picked up by the dogcatcher as a stray when he was very little, implying that they either died or Crosswise ran away.
Subconsciously Crosswise associates being bossed and ordered around, even being insulted, with being loved. Since Pongo and Perdita are most certainly NOT like that he doesn't feel that they really care about him especially since he's just one in a crowd and they're fairly impartial to all the puppies.
Crosswise is intelligent and capable but completely lacks the ambition or initiative to do anything with his gifts. He consequently feels bored and isolated with nothing to do. Extremely lacking in self-esteem, Crosswise can only validate himself through the approval of others which is hard when no one evens knows your name.
When Tic-Tac recalled his name on his first try, Crosswise was stunned and immediately latched onto him. He's been there ever since. Tic-Tac gives Crosswise the purpose he's been sorely lacking: being a henchman/labdog. Crosswise gets to use his intelligence to carry out the designs of a (evil) genius. Crosswise doesn't have to come up with any plans, merely execute them. This suits hm just fine. Tic-Tac's high-handed nature in dealing with his underlings gives Crosswise the attention he needs and makes him feel special after all Tic-Tac only associates with him and Dipstick. Better to be one out of two than one out of ninety-nine! Of course, Crosswise is a little jealous of how Tic-Tac dotes on Dipstick despite the latter's idiocy, so Crosswise keeps trying to show him up.
Crosswise admired Tic-Tac's genius and eagerly plays the part of his lackey, calling him 'sir' or 'boss' as needed. However Crosswise seems to either underestimate or ignore Tic-Tac's evil nature and treats his rivalry with Lucky as more of a sort of game than a real life-and-death struggle for dominance. He's sincere in wanting Tic-Tac's plans to work and really dislikes Lucky but tends to be a bit squeamish about death. Ironically, Crosswise is rather fond of Cadpig and has a crush on Two-Tone and so tends to leave them be.
While he isn't aware of all the details of Tac's life, Crosswise wants to be there to help him. He wants to be as close to Tac as Dipstick is and be there for him. Of course, if Tac sees him as a friend is debatable.
He's an averaged-sized puppy with his lower legs, both ears, and the area around his eyes covered in black fur. His spots form a criss-cross pattern on his back, hence his name