if I remember correctly, Marowak + Kangaskhan were originally designed as mother and father-type figures to the baby pokemon in its pouch long, long ago..
the baby theme in pokemon when it was reviewed for final release back then was considered an inappropriate theme so they took the baby out of the game, made marowak a basic evolved form (cubone) and changed it's type and altered its physical appearance from the first design.. where the 'baby' of the two remains as a file in-game, they already messed up and couldn't remove the pokemon file from the game's programming and thus Missingno was born. Looking closely for those who are interested in specific pixel sprites, the pokemon sprites from pokemon Green for both Marowak and Kangaskhan are quite similar and missingno contains the colors scrambled from the original baby design into an unrecognizable shape (but is still considered a pokemon file and a glitch..) but, yeah.
the moar you know, i suppose.