In an interview on "GMA," he said his brief appearance in "The Force Awakens" was "the most elaborate entrance of my career."
"Everybody talks about me for two hours -- it was a shock, it was a big surprise," Hamill said. "But, I think there are much bigger surprises in 'The Last Jedi.' In fact, the most important line Luke says is, 'This is not going to go the way you think,' and when I read the script I was stunned."
Hamill said "it's wonderful to be associated" with the new generation of writers and producers who grew up watching the original films as fans.
"These films now are being made by people that were children when the first films came out. They're the generation that grew up as fans and now are in charge of the franchise and it's just wonderful to be associated with something that makes people so happy and is escapism," he said.
Hamill admitted that his children are not the biggest Luke Skywalker fans, and recalled one conversation he overheard between his sons, Nathan and Griffin, and their friends.
"'It must be so cool to have Luke as your father,' and Nathan goes, 'Luke Skywalker doesn't tell you to clean up your room. And do your homework,'" he said with a laugh.
"We thought if they do another trilogy it wouldn't involve any of our characters. It would be all new characters. So I thought, 'Well, it's all or nothing. It's got to be Harrison and Carrie and all of us,'" he said.
But he was pleasantly surprised when he heard the news that both signed on for the new movies.
"I said, Harrison will never do it. He's so accomplished and, you know, I thought for sure that he would say no. When I read in the paper he signed, I said to my wife, 'Well, I've been drafted,'" Hamill explained.