at the menu screen, if you click on the gun that's on the treasure chest, a UFO will come out and zap up that gun! So far, the only one I've found. It's a reference to the company that makes the game.

at the menu screen, click on the frog and then his eyes will follow your mouse curser! Click on him again and he'll stop. But wait! There's more! If you roll your curser over the words: Adventure - Gauntlet - Options - More Games - Quit : notice that each one makes a different sound? And in that order, the sounds sound like the notes from Close Encounters! Okay, so roll - not click! - over the words/notes in order 3 times in a row and watch what happens! Also, after you get that to happen, click on it and you'll get another little surprise! Click on "whatever" to get out of it. Whew!