The literal meaning of the song "Birdhouse in Your Soul" by They Might Be Giants wasn't obvious to me as a young teenager. My mom suggested that it might be about a night light, and I've been kicking myself about it ever since. It seems obvious in retrospect.
The biggest clue is in the chorus. "Blue canary in the outlet by the light switch / Who watches over you." We're talking about a little blue night light in the shape of a canary. Other similarly simple clues abound. The little blue canary has a secret to tell from his "electrical well". He even tells us that his "name is blue canary one note spelled l-i-t-e." The canary tells us that it's "a little glowing friend," but reminds us that it's "not actually your friend." I have found that They Might Be Giants lyrics frequently combine simple metaphors with literal discussion even when they're in direct odds with each other.
The rest of the song holds with the theme of a night light, but many of the references are obtuse enough that they don't appear without a little bit of study. The blue canary speaks to the room saying that it must "filibuster vigilantly," which sounds to me like it's keeping the darkness and the possible monsters at bay not by getting rid of them, but just by putting them off until later. The little light even describes parts of the room around him. "There's a picture opposite me / Of my primitive ancestry." What sort of ancestry would a night light have? Maybe some other light that provides safety in the darkness. Perhaps a lighthouse? And indeed the song continues: "Which stood on rocky shores and kept the beaches shipwreck free."
The rest of the song is filled with all sorts of little references sometimes only tangentially related to the main story of the little blue canary in the outlet. References to Jason and the Argonauts, the Longines Symphonette, and guardian angels can all be found. I find that many TMBG songs are written in a similar vein. There's a simple, obvious subject to be found, but it's shrouded in allusion and metaphor to the point where it's not at all clear what's being sung about. Combined with the fact that not every Giants song even has a cohesive meaning (note "Particle Man"), this can make it even harder to decipher what's going on. On the whole, I find it worth the effort.