as defined by the reality TV show Forensic Mysteries on HLN, this a synonym phrase for "not the brightest person around"
boy 1) yo come to my backyard, i want to start a party by going out to weed
boy 2) are you an uptard, your dad, or mom will notice.
boy 1) nope my mom is not even home from work and my dad is not the brightest lightbulb in the chandelier, he will think we are trying to burn Cheetos on the barbecue or something.
A lightbulb tan is a tan gained from spending lots of time under a lightbulb. It usually results in people who are abnormally white. People who have lightbulb tans live in places that are in the middle of nowhere, are usually completely antisocial, and seem to never come out of their bright caves.
The thing that appears above your head when you think to yourself, either silently or out loud, "WWJD?"
When you suddenly have a thought of remorse or guilt, the moment the lighbulb appears above your head, (only this time with a vision of Jesus in it with his hands held out and that puppy-dog look in his eyes...) that makes you stop and rethink your actions and the repercussions of those actions.
Dude: "Hmmm... I probably shouldn't have pocketed that $20 that just fell outta that lil' ol' lady's purse...."
(Result: Jesus appears in a lightbulb above wrong-doer's head).