Which episode has the ‘origin story’ for Pinkie Pie. Where she lives with her family collecting rocks till she sees the sonic rainboom? (sonicrainboom?)
I believe Pinkie’s origin comes up in a couple episodes, one of which is the Cutie Mark Chronicles. I honestly had to consult the wiki. My pony knowledge is not what it once was…
Hope this helps! 
That’s the one. Thanks!
“And that’s how Equestria was made.”
Rock Farm, LOL