I'd be Pinkie Pie, and promptly break the 4th wall by visiting this site, and telling you all to obey me, as Pinkamena-Pills tells you to.
Or, perhaps, i would just continue to be Pinkie Pie, because if i am Pinkie, how would i know that i am me, the me that is here? How would i know im doing anything different from the Pinkie i know & see as me here, if i am her there? In the end i may not do doing anything "differently", because i am Pinkie Pie.