Pregnant Powerpuff Girls is an ongoing meme. It officially began on October 14, 2013 when NealTS misinterpreted Yntec's portayal of the trio being obese as the three being concerned over Blossom's pregnancy. JoHammet followed up with a brilliant, if slightly disturbing panel. It acheived Top Game Status.

About four days later, a second game finished which featured five panels of Preggers Blossom. The game was once again brought into PPG territory by Sambchop, and featured another JoHammet panel. The comment section was once again lively, As with the game before it, it made Top Game.

Five days later, a third game involving impregnated powerpuffs finished. Unlike the first two, this one started out with that topic in mind, Also unlike the first two, it included a pregnant Bubbles and Buttercup as well as Blossom. NealTS was mentioned. Sure enough, it also hit Top Game.
PPPG Bubbles

Rattle Me Bones! (original game)

OMG I am pregnant. But who is the father?

Oh no! Not another pregnat power puff game!