The gang, now seniors, meet with guidance counselors; Jim and Cindy Walsh announce that only one child can go to private college.
London moves into Maddie's house; Zack and Cody wonder if they were mixed up as babies.
Cody competes in a spelling bee against someone who loaned money to Zack.
The twins investigate Arwin's invention and find themselves in another dimension.
When Mike turns into a couch potato, Molly decides to go out of town with her sister.