If your printers all run through a centralized HP jetdirect print server, then you might have logs depending on how that server is setup. contact whomever runs that device.

From my own investigations, there are no 'access logs' on the printers, and no way to track it unless your specific network does some sort of logging. If your printers are set up individually like in most cases, then you don't have anything, really.

This is a interesting point though! I know that printers at Western Kentucky University and Northern Michigan University have both been displaying this message. From the other comments there are more people experiencing this.

It's not a meme that I know of, and there's no real connection between affected areas. This points to it being an automated process of some sort. Probably one that spams telnet ports hoping to find an unprotected printer.

What I'm getting at is that you do not have a specific prankster to hunt down, but a virus/worm, one that may have infected many machines. I'd guess it to be somebodies april fool's prank. I know at least some of these affected printers were behind a NAT, so it makes sense that the commands came from within the network, and given the relatively wide geographical area of effect, it must either be a group of coordinated individuals doing something completely inane, or it's a program.