Cubone/Kangaskhan connection with Missingno.? | Bulbagarden

Yeah, this is nice and all, but it's not true. Firstly, Missingno and 'M aren't the same thing - Missingno is actually a group of 'filler' Pokemon for unused index numbers in the code (for some reason, the programmers used index numbers of 1-190 despite there only being 151 Pokemon, hence there are gaps in places). 'M is at index number 0, and is also the one that 'evolves' into Kangaskhan, due presumably to Kangaskhan's very low index number (2).

The stated theory doesn't gel with how index numbers are known to work. Even if GF did want Marowak to evolve into Kangaskhan, there's nothing in the game's code that would suggest it.