Batman: Arkham Knight - 15 Hidden Easter Eggs, References & Secrets You Need To Find

11. The Gray Ghost Poster

In any of the opening clock tower segments, you can come across a number of cool art assets alluding to the wider Batman mythos - but one that really stands out is the poster for The Gray Ghost. Although the artwork looks to be referencing another DC character, The Spectre (or ancient precursor detective The Shadow), the very name 'Gray Ghost' refers directly to an episode of the animated series where Adam West made a legendary cameo. As the 1960s Batman is available as a skin in Arkham Knight too, it's a pretty neat convergence of all the various 'Batmen' there have been over the years.