The egg activity is explained here. The gist is that my teaching partner and I each have an egg (one is brown, one is white) and we try to persuade that our egg is better. In the end, no matter who was more convincing, the children find out that the eggs are exactly the same on the inside! They love it and it really hits home with them.
One last thing! My students LOVED this rap video that helps explain who Martin is pretty well!