It's from British comedy. This guy would ask another guy where the blank was. The second guy would say "I am the blank." And the blank could be anything. :{
SO THERE I WAS ON IMGFLIP.COM, SCROLLING PAST TEMPLATE AFTER TEMPLATE, WONDERING JUST WHAT IN THE SAM HILL I WAS GOING TO MEME ABOUT TODAY. THEN IT HIT ME, FOLKS... I AM SAM HILL