Check here for more from GamesBeat’s 12 Days of the Best and Worst of 2013.

Every year, game developers hide secret content in their titles for eagle-eyed players to find — like John Romero’s severed head  in Doom II, the elusive “green ninja ” in Mortal Kombat, and a creepy half-naked man  in Halo 2. 2013 is no exception.

Browse through the gallery below to see 10 of the coolest, silliest, most amusing Easter eggs of games released in the last 12 months.