Many of the details surrounding James Garfield's "assassination" (and Alexander Graham Bell's attempt to save him) are historically accurate.
After Pearl sees the staff eating human flesh she calls Otto. Just before the split screen wipes you can see a big blue paw print on the clock on Otto's desk. This is a nod to his previous gig as the original host of the children's show "Blue's Clues".
Otto (Steve Burns) is most always wearing something blue or something with blue in it, possibly an homage to Jeu de Bleue (1996).