Wednesday was invited to the school science fair. Her family was there watching her too. She was confident about her project. She made Uncle Fester mixed DNA with Socrates. Uncle Fester eats everything. Wednesday gives him a Rubik's Cube without the DNA and he ate it, but with the DNA mixed, he didn't eat it. She sees the other kids' projects and thinks they're lame. She thought she was winning, but the announcer said, "As long as you tried, you get a prize!" It makes Wednesday ask, "How will you win if nobody is losing?" Everybody ignores that and so her family goes home with her.
When Wednesday and Pugsley don't come to dinner, their parents worry about them. Gomez thinks the family isn't close enough, so they take a three-week road trip all around America. Before they leave, a strange-looking man comes to them saying, "A girl here named Wednesday Addams was switched with another baby when she was born; the father found her and decided to take DNA of her to see if she was his daughter." The parents say that Wednesday is an Addams and start the trip.
Unfortunately, the man follows them. Gomez and Morticia try to avoid him as much as possible and not let Wednesday know. However, Wednesday knows something is wrong, and each time they travel to another place, Gomez's actions upset Wednesday more.
- As part of a cross-promotion, a CGI version of Progressive Insurance spokesperson Flo makes a cameo on a billboard the camper crashes through.
- Unlike in that last movie, after Wednesday is exposed to much sunlight, her skin remains pale.
- Thing wears a fingerless glove.
- One of the songs played on the radio of the Addamses' camper is Gordon Lightfoot's "The Wreck of the Edmund Fitzgerald".
- Oscar Isaac as Gomez Addams
- Charlize Theron as Morticia Addams
- Chloë Grace Moretz as Wednesday Addams
- Javon 'Wanna' Walton as Pugsley Addams
- Nick Kroll as Uncle Fester
- Snoop Dogg as Cousin Itt
- Bette Midler as Grandmama
- Bill Hader as Cyrus Strange
- Wallace Shawn as Mr. Mustela