In a twist of fate, Coogan discovered an unexpected familiarity with the role of Kenny. “The timing was weird because a friend of mine and I had been messing around with a video camera, filming this little cooking sketch we had about two stoners who could barely get through grilled cheese sandwiches,” he said. “It was like I had been working on the character before I even knew it existed. We had taped the first one two weeks before the first audition for the movie, so I had the torn jeans, a skull vest, $15 wigs — they were terrible looking. Maybe that's why I was drawn to him.”

After his audition for Bryan, which, to his recollection, did not go well, Coogan went to his car, put on the stoner costume, and barged back into the audition room. “I kicked the door open and was like (affects stoner voice), ‘All right, who's in charge here?’ I was just Kenny. The producers were like, ‘Yeah, you got this.’”

The Crandell family was rounded out with Concetta Tomei as the absentee mother, Robert Gorman as the TV-obsessed youngest sibling Walter, Christopher Pettiet as the lovelorn middle child Zach, and Jennifer Love Hewitt as tomboy Melissa.

“We cast Jennifer Love Hewitt and [Kids Incorporated] wouldn't let her out to do the movie, so I quickly brought people in,” Bialy said. One of those last-minute potential Melissas was Danielle Harris, a young actor who had made a name for herself playing Jamie Lloyd in Halloween 4: The Return of Michael Myers and Halloween 5.

The New York-based Harris had just landed in Los Angeles the day before to audition for other projects when the opportunity to read for Melissa presented itself. “Back in the day, all of us kid actors would come out with our moms for pilot season — when pilot season was a short amount of time; now it's all the time,” she recalled. “The day after I arrived I met with an agent to represent me in California and she was like, ‘I love you, I want to sign you and — actually — I've got something I think you would be really right for, so we should see if we can get you in today?’ I was like, ‘I already have an audition?’ It ended up being for Don't Tell Mom. I swooped in, went on tape, and ended up getting the job that day.”

With the cast locked in, production began in and around Los Angeles during the summer of 1990 and it soon became clear to everyone on set just how much of a star Applegate was going to be.