10 Games Hidden Within Games
5. Ninja Gaiden Trilogy (Ninja Gaiden 2004)
When Team Ninja remade Ninja Gaiden for Xbox in 2004, the purists were happy. Not only was the update as insanely difficult as its NES predecessors, it included the original trilogy as an unlockable Easter egg.
The initial release allowed players to pit their skills against the brutal 8-bit editions of the first three games - seriously, Dark Souls feels like easy street after playing through these - but subsequent versions included different unlockables.
For instance, the Ninja Gaiden Black update did not feature the original trilogy, though the arcade version of the first game was included in their stead.
The 2004 game was actually a prequel to the NES titles, so those who played it through to completion before unlocking the original games got to experience the story in chronological order, but they took some punishment along the way.