Worms 4: Mayhem Tips

Easter Eggs
Back To The Future:
Level: Serve and Destruct (level 5)
What to do: See the Back to the Future-ish looking car? Chuck a grenade (or owt, really) at it and 2 streaks of fire appear on the road.

Hidden Room:
Level: Nice to Siege You:
What to do: Go around the back of the castle and you will see a cave. Go in there and there will be a cut-scene of the hidden room with a worm with rabbit ears screaming

Hidden Diamonds:
Level: Carpet Capers
What to do: The Diamonds are in the tower that "Egg" is standing on. Parachute down to the collection of weapons near him and use Girders to get into the tower.