What really happened at the end...SPOILERS!
Just before the creature behind Sam was able to get to him, Barney the dinosaur descended on the Great Space Coaster and saved Sam and his father, and a crispy Louisa, though they later discarded her at a recycling facility, as she resembled plastic. Helping Barney was the Dandelion People, who have been secretly fighting the walkers for centuries.
But what is really groovy is that the Dandelion People also captured one of the walkers. They all then went Denny's, where the Dandelion People leader began a dialog with the walker, who he found out was named Harry. After quite some time they came to the conclusion that they can live together in harmony.
The walker finally understood that killing people, turning others into similar creatures, and mating with young human females is not a very nice thing to do. He felt bad and, in turn, asked to go back to the house and talk to all of the other walkers.
Having done so, and having convinced the other walkers of the errors in their ways, they got on their space phones and called all of the other walkers on earth to explain the situation. They all decided that it was true that we can live together in harmony.
Since that time, on the date of the agreement, many walkers, humans, Dandelion People and Barney get together at the Ramada and listen to Barry Manilow tunes. At the third anniversary party they brought Louisa back, although she was a regenerated version and smelled a little funny.
The plural of mouse is mice. The plural of goose is geese. Why is the plural of moose not meese?