I remember something interesting from the message board on Crichton’s official website in March 2005. (No longer, so no link) When a new member kept referring to Michael Crichton as “Mike”, the administrator posted this:
…he really doesn't like the "Mike" thing. His name is Michael. Just a little FYI. [As his publicist, I get people calling me everyday saying, ‘Ya, this is Mike's good friend, so-and-so.’ That's a HUGE red-flag that they've never met him. It's usually pretty funny when I say, "Actually, I don't think you are." Then the sputtering starts. It just makes me laugh.
When I participated in a November 2005 online discussion with Crichton through Barnes & Noble, the moderator started the discussion out by calling him “Michael”, therefore setting the tone.
I tended to address him as “Dr. Crichton” because I prefer to be more formal with people I don’t know personally. And as a sign of respect. But I addressed him as “Michael” during the discussion.
Crichton did go by “Mike” when he was younger. According to the book First Words, Crichton was known as “Big Mike” in high school.
And Crichton’s sophomore high school yearbook—the 1958 Harbor Hill Light—lists him as "Mike Crichton". He was a sophomore class officer and in the Rocket Club at Roslyn High School.
Crichton played basketball at Harvard and three articles in the student newspaper Crimson refer to him as “Mike Crichton”. (The articles also wrongly put his height at 6’8”—one inch short.)
December 15, 1960
March 8, 1961
March 21, 1962
In the 1964 Harvard College yearbook (Crichton’s senior year) he is listed in the index as “Crichton, John M.” His full name was John Michael Crichton but as his father was named John, I’ve seen no evidence that he was ever called John.
Before The Andromeda Strain was published in 1969, when he wasn’t writing under pseudonyms, Crichton wrote under the name “J. Michael Crichton.” One article, a 1968 review of Kurt Vonnegut’s Slaughterhouse Five, was reprinted in the book The Critical Response to Kurt Vonnegut.
Many people, when they get older, decide to drop nicknames. But family has its privileges. Crichton’s brother Douglas called him “Mike”. From a New York Post article after Michael Crichton’s death:
Douglas Crichton recalled watching the sci-fi classic "Forbidden Planet" with his 6-foot-9 big brother, who used that inspiration to build a robot at their childhood home in Roslyn, LI.
"Mike was remarkable from the day he hit the ground," Doug Crichton said.
In his autobiography Travels, Michael Crichton recounted a conversation with his brother in which Douglas called him “Mike”. (p. 175, hardcover edition)