Perhaps the letter is an invitation to a Christmas party and the cat and dog want to be part of the fun. They chase it, causing all sorts of chaos and comedy along the way.
The story might involve the cat being smart and finding ways to outwit the dog, or the dog being persistent and never giving up the chase. There could also be unexpected turns like the two becoming friends in the end.
It could be that the cat took something the dog wanted, so the dog is chasing to get it back. Or perhaps the dog is instinctively chasing the cat as part of its hunting behavior.
Maybe the dog is just playing or thinks the cat has something it wants.
It could be quite funny and chaotic. Maybe the cat is agile and determined, while the dog is confused and trying to escape.
The scene of a cat chasing a dog in a cartoon can be very exciting. The cat might be leaping and pouncing, while the dog is frantically trying to escape. There could also be some funny sound effects to add to the chaos.
It could be about the friendship and adventures of the cat and dog during Christmas. Maybe there's a quest to find the perfect gift or save Christmas from some sort of mishap.
It might show a funny and chaotic scene with the dog running after the cat, maybe in a backyard or a street.
It's usually about a mischievous cat trying its best to catch a clever mouse, full of fun chases and tricks.
It could be a cartoon where the cat and dog are helping Santa Claus deliver presents.
It could be a cartoon where the dog and cat are decorating a Christmas tree together.