Don't own Ranma 12 or Alf. Just a thought for a silly one shot. Alf meets Ranma.
Melmac One Half

Ranma was pretty happy. The Kunos were all committed to an institution and Happosai had been arrested and hauled off to another planet by the galactic police in a block of carbonite for groping an alien princess named Ayeka. Pantyhose Taro had picked a fight with Shampoo and had defeated her after knocking Ranma out with a strike from behind. Now, Shampoo was chasing Taro and Mousse was chasing them both. Ukyo had married Konatsu. A car driving through a mud puddle in front of Akane splashed Ryoga. Now he was in the hospital getting skin grafts from his butt to his head because she decided to scalp him. Ryoga's scalp now decorated Akane's mallet handle. Since then she had avoided bashing Ranma and they had actually gone on a couple of dates. Life was good, then Murphy farted.

The skies were ominous with odd sorts of lightning and odd colored clouds. Ranma and his father were sparring a.k.a. pound the panda. Akane was watching the two go at it from the porch when the panda man got a lucky shot with his foot and knocked Ranma into the pond. A red headed Ranma jumped out of the pond when what sounded like a thunderclap knocked her and her panda father to the ground. Akane saw what happened. An egg shaped object had crashed into the pond and arcs of electricity were flashing across the thing's surface. Gradually the light show died down and a hatch opened up on the part above the waterline.

"Ranma!" Akane called out. "There's something in the pond." The two approached what now looked to be a small space ship resting in the koi pond. The red head went over and looked in an jumped back. "Gahh! Its Cologne's brother." Akane peeked in and said, "Ranma, you baka, its just a cute furry alien. Don't pick on it!" She then whacked Ranma lovingly in the forehead with her hammer, leaving an odd shaped bruise. The girl picked up the creature and carried it in to the couch in the living room. The families gathered round and stared at the strange being that had fallen into their midst.

The creature groaned and muttered, "Man, I shouldn'ta cut the corner around that last beacon. Hey, this ain't the Tanner's place!" Then it looked around the room at the Tendos and Saotomes and settled on Ranma chan. "That mark!" looking at the bruise on Ranma chan's forehead, "Hey princess. Don't get mad. It was just laying there and I thought nobody needed it any more. Here you can have it back. It then tossed a short rod at Ranma. She caught it and suddenly, under a compulsion, held it up and shouted, "Melmac planetary power make up" then a sound like a 1957 chevy backfiring and starting up came from nowhere. She was lifted up into the air and her clothes vanished, showing everyone that she didn't use henna. Some sparkly lights appeared and she came to ground wearing a shiny silver plastic bikini and a ceramic tiara. Ranma realized that she was now holding a ceramic baseball bat with little cat shaped marks in a line down one side. The creature bowed low and said, "Hail princess China, Senshi of Melmac. You have returned after being missing since the Corelle Millennium!"