Eggs It Through The Giftshop -- Click on all the fruit in the tree in the Underworld (next to the pool of water).
Hint 3
Egopus Rex -- Spell out ATHENA (A, Th, H, N, A) on the name puzzle in the secret tunnel door. You can only do this after you get the Greek alphabet page but before you finish entering the actors' names.
Deus Egg Machina -- Use the blacklight on Charon's lantern. The only time you can do this is after you fix the lightboard and get the ultraviolet light, but before you use the blacklight on the vase.