Buffy's relationship with Spike in the comics varies. Sometimes they have significant interactions and may even be romantically involved, but it's not a constant throughout all the comic series.
Well, Pinkie Pie is also a likely main character. She would be the one to throw a big 'Welcome to Pony - hood' party for Spike. She could also introduce him to all the fun and wacky things about being a pony. Rarity could be involved as well. She might take it upon herself to give Spike a makeover in his new pony form, making him look dashing and stylish among the ponies.
I'm not sure specifically what the'spike story' is as the term is rather general. It could be about a character named Spike in a particular movie, book or TV show. Maybe it's about a sudden increase (a spike) in an event or situation and the story around that.
It varies from comic to comic. Sometimes they have a romantic connection, while in others, their relationship is more complicated or not existent at all.
The status of Spike and Buffy's relationship in the comics varies. Sometimes they are shown as a couple, while in other instances, their relationship is more complicated or undefined. It all comes down to the particular comic series and its plot.