This stage is banned in both Japanese and American tournaments due to its overly large size promoting excessive camping, and the random Pokémon hazards disrupting gameplay. Ness also has a huge problem recovering here; it is impossible to recover between the buildings should he fall in.
Layout and Pokémon
Saffron City has one main platform attached to a small platform above a door. To the right is a narrow platform and to the left are two elevators (moving platforms). Between these and slightly lower than the other platforms is yet another narrow platform. There are many gaps in-between that character and items can fall into. It is this feature, as well as the fact that it is a stage upon the tops of tall buildings, that makes it similar to the Fourside stage in Super Smash Bros. Melee.
Every now and then, the door of the Silph Co. building opens, and if the door has been open for a while or if a character approaches the door when it is open, one of five Pokémon will emerge from it. These Pokémon are:
Flying Pokémon, including Butterfree, Pidgey, and Fearow, are occasionally seen flying across the background and may also appear in swarms. Though it is very rare, Moltres sometimes makes its way across the background. Moltres is one of the easiest to spot of these Pokémon, as it is bright orange.
Saffron City made its first appearance in Pokémon Red and Green (later released as Pokémon Red and Blue outside of Japan). Saffron City is the second largest city in the Kanto region after Celadon City, and one of the largest cities in the entire Pokémon universe, alongside cities like Goldenrod in Johto and Castelia in Unova. The main building of Saffron City, Silph Co. is a major producer of items to benefit Pokémon trainers, producing items such as the Master Ball and the Up-Grade, and it is the rooftop of this building that forms the main platform of the Saffron City stage. In Pokémon Red, Blue, and Yellow, the entire city was taken over by Team Rocket, mainly Silph Co. The player needs to stop them there in order to prevent Giovanni, Team Rocket's leader, from getting his hands on a Master Ball.
The music heard in this stage first originated from Pokémon Red and Blue's opening sequence and title screen.
Description from the Instruction Booklet
Wild Pokémon appear in the middle of the city to attack the fighters. It's best just to stay out of their way.