UN : Umbrella Nutcracker
EU : Egg University
NATO : New Astronautical Telemarketing Orange
ASEAN : Arsonist Seagull English Apple Natives
SAARC : Surfing Ability Award Rooster CraneBRICS : Brick Raining Icy Coffee Sea
ISRO : Iguana Saw Rat Ostrich
WHO : Watermelon Hugging Ovary
These are the ones I can remember for now-