Back in the days of the 4th Generation, Serebii Joe of serebii.net released confirmed info. (Which was bulls**t, even at the time people knew it was wrong.) Such as Shellos evolving into Lapras, and some other information I cannot think off the top of my head.

Recently, he has confirmed questionable information. The three starters of the 5th Generation (Black & White) have final evolutions that were leaked onto a Japanese image board.

Meanwhile, back at 4chan. /vp/ is a complete clusterf**k, with people trolling each other, saying these are real/fake- Those who state it's real, say it was confirmed by Serebii, those who do not, say it was confirmed by Serebii.

Thus, this meme was born.

So basically, when anyone says something is fake, someone will follow up with something along the lines of "Serebii confirmed it! It MUST be real!" and then send the thread into hell.