Blank check is a minor /b/ meme that was first posted 2006/03/05, featuring a character who was drawn on 2005/05/14, but with the face erased. It came with the message "I've given you a blank check, go crazy". Within an hour, over 100 different faces were given to the image posted.
The image was most likely given the name Doppelgänger from the Sandwhich guy post with the text, "Nice try Doppelganger! Save it for Queen Doppelpoppolus!"
Doppelgänger is literally a window to the past, in that you can look at the memes of old through it.