Technically, I first started roleplaying on Club Penguin, but I wasn't aware I was RPing at the time.

I truly first started RPing on the Barnes and Nobles NOOK, starting with a random Warriors RP Clan called AshClan.  A lot of RPs on the Nook are super disorganized (expected when working with a review format).  There was godmodding, autohitting, bunnying, Mary Sues, and puppeting galore on the NOOK.  Most of my RP horror stories come from my time on the NOOK, actually.