>>28982730Because... it looks like Pikachu? What defines a Pikaclone BESIDES looking like Pikachu? You can't use the fact Marill is part Fairy to disregard the obvious. Pikachu was a 2 stage mono type mouse pokemon (Literally the "Mouse Pokemon") that later got a baby form. Marill was a two stage mono type mouse pokemon (Literally the "Aqua Mouse Pokemon") that later got a baby stage. Both have the EXACT same facial structure besides Marill lacking the red cheeks, both have a zig-zag pattern tail that show off their typing (Pikachu's lightning bolt, Marill has a bubble/water drop on the end). You must have started playing Pokemon after gen 1-2 because literally everyone I know who has played pokemon since gen 1 considers marill a pikaclone.
Plusle and Minun were the start of the "one-stage" pikaclone trend and that was literally because a new gimmick in gen 3 was double battles, so instead of making one pokemon that could evolve they made two as "supporters". Why they continued with that trend past gen 3 is beyond me but the trend of gen 3+ doesn't invalidate Marills position as a pikaclone.