Originally, Mr. Mime was a pure Psychic-type Pokemon that wasn't part of an evolution line. With the creation of the Sinnoh region, Mr. Mime was given a pre-evolution, Mime Jr. Both of these Pokemon are exclusive to Pokemon Diamond. This has been carried into Pokemon Brilliant Diamond and Pokemon Shining Pearl, in which Mime Jr. and Mr. Mime can only be obtained in Shining Pearl via trading.