Metal Gear Solid 4: Guns of the Patriots Easter eggs

Snatchers reference
The suit Snake wears in Act 3 is a homage to Gillian Seed, from Snatchers.

The "Dr. Madnar" mentioned in Act 3 is a reference to a scientist from Snatchers. The Scientist "Dr. Madnar" is the scientist responsible for the original Metal Gear (NES)