Sean Astin had been acting since he was a child and was best known for his role as Michael "Mikey" Walsh in the American adventure-comedy The Goonies. Astin most recently played Frack in The Witches of Oz, directed by Leigh Scott
While working on The Two Towers he persuaded a number of fellow cast and crew members, including director Peter Jackson, to act in or work as crew on his short film, The Long and Short of It (2003), which takes place on a street in Wellington, New Zealand. The film premiered at the Sundance Film Festival, 2003, and appears on the "standard edition" DVD of The Two Towers as an extra feature together with a "making of" video.
Sean is the son of actress Patty Duke and was born Sean Patrick Duke, but took the name of his adoptive Father, John Astin. Sean is the older half brother of actor Mackenzie Astin, the two recently starred opposite each other in the movie The Final Season (2007)- In which Sean's character's lover was played by Rachael Leigh Cook, an actress whom had also played the lover of his Lord Of The Rings co-star, Elijah Wood, 8 years earlier in the movie The Bumblebee Flies Anyway.
Sean has been married to Christine Harrell since 1992. They have three daughters: Alexandra (b. 1996), Elizabeth (b. 2002) and Isabella (b. 2005)- they all share the middle name of Louise.
Sean's eldest daughter, Alexandra (Ali), made a cameo appearance in The Return of the King as Sean's character Sam's eldest daughter, Elanor the Fair.
While filming the Fellowship of the Ring, in the scene where Frodo leaves the fellowship to go to Mordor on his own, while Sean was walking towards Frodo's boat, he stepped on a shard of glass that pierced his foot. 24 hours and many stitches later, they were back filming.