Here comes a special boy here comes a special boy here comes a special boy here comes-

Anyway here's Spring Cheer, the son of Pinkie Pie and Cheese Sandwich! His coat definitely wasn't what his parents were expecting, but one look at that mane and those eyes and you just know who he belongs to. :')

Backstory: After wandering around Equestria for years throwing parties, Cheese decides to come back to Ponyville to throw a big party for Pinkie's birthday. As it turns out, Pinkie was throwing her own party for herself and they had lots of laughs over it, and decided to combine their ideas to make a huge extravaganza. They end up being some of the last to leave, just talking for hours over cake and milkshakes. Pinkie invites Cheese to hang out for a while, and he agrees, admitting that while traveling Equestria is fun, it's rather lonely. Pinkie asks about Boneless II, and Cheese says he's not very talkative.

In the end, Cheese decides to stay with Pinkie and works with her in the bakery, and Sugarcube Corner expands its menu to include specialty cheesecake and the occasional sandwich. The two marry and have a son.

As for Spring Cheer himself, well. He's a very energetic Earth pony who walks with a clear spring in his step. He enjoys parties just as much as his parents, but soon finds that he's not that good at actually throwing them, preferring to instead just attend. He finds a knack for providing the food though, and it lights up his day when he sees his treats bring a smile to everyone's faces. It's when he realizes how much he loves baking for others that he gets his cutie mark. He begins catering parties and other events all over Ponyville and may even expand beyond one day, but for now, he's right at home in Sugarcube Corner with his parents.

Unsurprisingly, Spring gets along very well with Firestarter, as both are prone to silliness and they understand each other's humor. Unfortunately Firestarter isn't that great in the kitchen, so Spring doesn't tend to let her cook. At least she agrees this is for the best.

So yeah, that's Spring Cheer! Pinkie and Cheese's happy boy and they would both die for him.