This one came to me pretty easily. If the ponies of G4 and G5 met each other, you can believe Pinkie and Izzy would instantly get along with each other. They're both bouncy, energetic, affectionate, kind-hearted, and they love making ponies happy: Pinkie through her parties, and Izzy through her unicycled crafts. I dunno if either Ponyville or Maretime Bay could contain their combined energy, tho, lol.