3TrainerPoké $

3TrainerPoké is the Pokémon Yellow version equivalent of 'M, and can only be obtained by trading an 'M from the Red/Blue versions to the Yellow version. When the Red/Blue versions were released, the east coasts of Cinnabar Island and Seafoam Island were reprogrammed to disallow random encounters. However, some time after Yellow was released, a new glitch was discovered that allowed battles with any Pokémon, including 'M and Mew. This is explained in the Glitch Guide on GameFAQs' Pokémon Yellow page

When encountering 'M in Pokémon Yellow, its name appears as "File:3trainerpoké.gif," although it is generally referred to as "3trainerpoké" for the same reason File:Msglitchname.gif is referred to as "'M." or "M block". 3trainerpoké is different from the 'M of Pokémon Red and Blue: its attacks are Bubblebeam, Poison Sting, and Comet Punch. At level 1, it learns Waterfall, Waterfall (again), Comet Punch, and Vicegrip.^{[citation needed]} If encountered in the wild, it is Poisoned when it first appears. Like 'M, 3trainerpoké glitches the game in various ways, can evolve into a Kangaskhan or Rhydon, changes level and stats seemingly at random, and occupies slot 0 in the memory. ^[1] This is why trading an 'M to Pokémon Yellow will result in a 3trainerpoké. Also, 3trainerpoke is seen as #176 when its stats are viewed.