"When I came into this, I hadn't done much with an audience," Gordon-Levitt told ET on set. "Most of my stuff has been one camera stuff."
Gordon-Levitt played the role of Tommy on the series, with actors John Lithgow, Kristen Johnston and French Stewart rounding out the ensemble.
"My character is Tommy, and he is the oldest alien -- the old, wise alien, and the father figure to all this aliens -- who got stuck in a teenage boy's body," said Gordon-Levitt. "He's this old wise man half the time, and the other half he's just a teenager, reckless and hormonal."
"It's excellent writing and I'm not just saying that so I can get more lines from the writers!" joked Gordon-Levitt. “This is just totally different and that’s my favorite thing about it."
Check out the video about to see a 14-year-old Joseph Gordon Levitt on set of 3rd Rock From the Sun.