From Wikipedia (Trivia and Goofs of This Episode)
* Playing 'London', Brenda Song had actually guest-starred in That's So Raven before as Amber in "A Dog By Any Other Name". So technically, Raven knows her as London Tipton and Amber, but where as Brenda is seen as London in that episode.
* Dylan and Cole Sprouse will be guest-starring in one of That's So Raven's unaired episode titled, "Here Comes The Twins", who will in turn be named "The Davidson Twins" in that episode. So technically, Raven knows them as Zack and Cody and Davidson Twins, but where as the twins are seen as Zack and Cody in that episode.
* Ashley Tisdale guest-starred in Hannah Montana along with Zac Efron and Vanessa Anne Hudgens as the crew of High School Musical. So technically, Hannah knows her as Ashley Tisdale and Maddie Fitzpatrick, but whereas Ashley is seen as Maddie Fitzpatrick in that episode.
* Even minor characters or notable guest-stars who are in no affiliation with the original cast of the shows, have managed to doubled their characters in the shows.
* Alyson Stoner, who played recurring role Max in The Suite Life, in turn played Ally Parker, a hollywood child star in one of That's So Raven's episode "Goin' Hollywood".
* In the same episode, Allie Grant, who played recurring role Agnes in The Suite Life, played Carly, Ally's advisor and cousin.
* Ben Ziff, who played Chelsea's date in an episode titled "When 6021 met 4267" played Todd, London's dentist boyfriend in "Cookin' With Romeo and Juliet"
* Moises Arias has been on episode Daycare of Suite Life as Randall and has been on Hannah Montana as Rico.
* Basically, guest stars starred in each show, and then when put together as one show, it makes it look like there are two or three of each person.