Multiverse

Throughout the series, multiple "dimensions" have been shown to exist in the Phineas and Ferb universe. These "dimensions" vary slightly or significantly from the canonical dimension where the main characters live.

Nature of The Multiverse
Although they are frequently referred to as "other dimensions", the "dimensions" of Phineas and Ferb in no way resemble real life theoretical dimensions. In real life, what defines a higher or lower dimension is the ammount of directions in which one may travel in them. Phineas and Ferb obviously live in the 3rd dimension, being able to travel sideways, backwards and forwards, and up and down. Other dimensions in the series always have the same ammount of directions, and are therefore also in the third dimension. They are, instead, seperate universes to themselves, but as Baljeet showed in Phineas and Ferb: Across The Second Dimension, they are connected by a stream of energy. Phineas and Ferb therefore live in a "multiverse".

Physics of The Multiverse
Until the TV movie Phineas and Ferb: Across The Second Dimension premiered, not much was known about the actual workings of the Phineas and Ferb multi-verse. In the film, 2nd dimension Baljeet gives a lecture on how one travels through the multiverse. It appears as though the "dimensions" are connected. There is a clockwise energy flow which connects each of the "dimensions". To travel into an alternate dimension, it appears that one must create a portal which accesses this flow of energy. Since the energy flows in a clockwise direction, acessing Phineas's dimension would require traveling against the natural flow of energy. Baljeet explains that while this is possible, it would require an enormous ammount of energy to travel in such a way. Initially, they do indeed open such a portal. However, it is unstable, and closes soon after Phineas announces he will not enter his dimension until he finds the now captured Parry.

Later on, Phineas is able to access his own dimension by travelling clockwise through the entire "grid" of "dimensions" in the multiverse until he gets back to his own.

List of Dimensions
(Help compiling this list would be appreciated.)