Gobliins 2: The Prince Buffoon

"In 1992's Gobliins 2 the player controls two characters: Fingus (who is well-mannered, intelligent and shy) and Winkle (who is dumb enough to not know how to push a button in the first screen, but who is almost terminally brave). They've been sent to rescue the King's son, the Prince Buffoon, who has been kidnapped by the evil Amoniak. Both goblins can pick up and use items, and both generally use an item in different ways. Unlike its predecessor, Gobliins 2 allows (and requires) the player to travel back and forth between rooms. Also, both goblins can be given an order simultaneously, allowing for the inclusion of timing puzzles. A significant difference between this game and its predecessor is that in Gobliins 2 neither playable character can die.

An easter egg is that Fingus, if left idle, will eventually whistle a short tune, and the tune is different in each room."

Source: Wikipedia, "Gobliiins," available under the CC-BY-SA License.