When a Pokemon who can evolve by level, evolves at lv. 100 from the stage you capture it, if his nickname is the name of another Pokemon, it evolves into said Pokemon, retaining gender, nature, ivs, evs, ability. The stats are these of the new Pokemon Species, and you chose the moves. The newly evolved Pokemon retains his egg group. So with this method you can get a full team of Arceus. BUT: The pokemon must have the EXACT same weaknesses and resistancies of the pokemon you want it to evolve. This method could be called... the 100RattArceus method: the name stands for LEVEL 100 RATTata ARCEUS.