Slide Pokémon
A slide Pokémon is a Pokémon used in arbitrary code execution, most commonly for Coin Case arbitrary code execution.
It is a Pokémon which has its data 'skipped', usually by having the code 'fall through' to the next Pokémon, hence the name "slide Pokémon".
It is often best to use a low level 'freshly caught' Pokémon without any bad IVs for this, although another type of slide Pokémon includes one with a jump or relative jump to elsewhere in the game's RAM.
This Pokémon is used when the program counter reaches in the middle of a Pokémon's data (such as Pokémon 3) but it is better to represent the desired code in the next Pokémon's data.
For example, Coin Case arbitrary code execution redirects the program counter to FA98 (essentially DA98), which is the second byte of the third Pokémon's attack stat experience. However it is better to have the code fall through to Pokémon 4, in which a Pokémon like Quagsire (C3; jp yyxx) can be used to redirect the flow of the code to somewhere better such as box names or stored PC items.