User blog comment:Disney & Nick fan/Another Across the 2nd Dimension Promo!/@comment-174.111.60.178-20110530213125/@comment-76.15.25.240-20110601104338

It's also possible they don't want to reveal every single alternate character in the movie. Revealing the alternate versions of Phineas, Ferb, Candace, Perry, and Doofenshmirtz is one thing, but they probably don't want to go to far by showing every alternater character.