It was a throwback Thursday for Joseph-Gordon Levitt when he appeared on Conan on Dec. 4.
Joseph started acting at 7-years-old, and by the time he was on Jeopardy! he already starred in tv shows 3rd Rock From the Sun, Roseanne and The Powers That Be as well as various movies including Angels in the Outfield, A River Runs Through It and Beethoven.
With his signature long hair, he was an energetic teenager. As O'Brien said before they watched the clip, "You're 16, but I love your enthusiasm."
In the 17-year-old video, Jeopardy! host Alex Trebek provided the answer to the question, "Holden Caulfield, the hero of this Salinger novel, hates movies, phonies, and his classmate Ernest Morrow."
But all that can be heard over Trebek's voice is an excited "Ooo! Ooo!" and that's Joseph's voice!
He knew the answer, "What is Catcher in the Rye?!" He then exclaimed, "I'm so excited! That's my favorite book!"
Just hearing Trebek's response, "Good for you," gave Joseph a good laugh as he reminisced on his game show debut.
While Joseph was already a celebrity before going on Jeopardy!, check out the celebs who were not famous yet before they appeared on game shows in the video below.