Well, I'm not sure of the specific 'angry grandpa christmas story' you mentioned. It could be about an angry grandpa during Christmas, maybe he was mad because the presents weren't what he expected or there were some family issues during the holiday. But without more details, it's hard to be more precise.
I don't know the exact main events as I'm not sure which 'angry grandpa christmas story' it is. It could be that the grandpa got angry because the Christmas tree wasn't decorated to his liking.
Grandpa's Christmas story began when he was a young boy. He woke up on Christmas morning to find a single small present under the tree. His family was poor, but that didn't stop the joy of Christmas. He remembered how his mother made a special meal with what little they had. As he grew older, he made it his mission to give his own family a grand Christmas every year. He'd save up all year to buy presents for his grandchildren. And every Christmas, he'd tell them this story to remind them of the true meaning of Christmas - not the presents, but the love and togetherness.
The 'angry alien christmas story' could start with an alien landing on Earth during Christmas. It sees all the bright lights and noisy parties. The alien, being from a quiet and orderly planet, gets really angry at the commotion. It starts to cause some trouble, like zapping the Christmas lights or scaring the carol singers. But in the end, it might learn to appreciate the spirit of Christmas through some kind of heart - warming encounter with a kind human.
In the angry elf Christmas story, perhaps the elf was angry because he had been overworked every Christmas. He was tired of the long hours and little recognition. One Christmas, he just couldn't take it anymore. He started to protest in the workshop, which made all the other elves stop and stare. Santa had to come and talk to him to find out what was wrong.
One interesting 'Angry Grandpa Ghost Stories' could be about his encounter with a ghost in an old attic. Maybe he was looking for something and suddenly felt a cold breeze and heard strange noises.
Grandpa is surely a main character. And since it's a Christmas story, there could be Santa Claus as a character too, if grandpa's story involves the magic of Santa coming to town. Also, his wife or partner might be in the story, sharing the Christmas traditions and joys with him.