When you become a child movie star, do 3 movies and then become not cute anymore. May also include heavy marijuana use and starting a band that covers Velvet Underground but makes them about pizza. Symptoms of McCulkinism include being booed off stage during a kazoo solo.
Bob: "Dude, Jim just stared in 3 movies, became not cute anymore and started a band that sings about pizza!"
Chris: "Do you think he McCulkined?"
Jim: "You guys wanna hear my kazoo?"
Bob & Chris : "BOO!"
Brandon was late to a meeting and mid way through asked a question that had already been answered. His boss called him out and said you would have known that if you were here on time. Afterwards his co-workers joked with him because he had been mcgurskied.