To put on my own nerd hat, the author is referencing "dat boi" as in "oh shit here come dat boi!" — not Pepe. Both are frog-related memes, but dat boi is much more recent and did originate on Tumblr, even if its final form may have actually come into fruition on Facebook — though Know Your Meme can be wildly inaccurate at times.
[1] http://knowyourmeme.com/memes/dat-boi