Brings to mind the phantom fungus picture* in 3.5e MM. "It's completely invisible! You can't even see it with invisibility purge. Oh, and here's a full color picture of it!"Invisible Stalker from the 2e Monstrous Compendium. Tell me that isn't the most amazing art you've never seen!
* To be fair, I really digged that picture, and phantom fungus, in general. But yeah.