>>18654262But the point of the tongue is that it also plays on its design! Ninja scarves served to both hide their identities, aid in climbing and to tie up when on tree branches for stability when sleeping. Greninja's can do that and more, considering that its prehensile and retractable.
As many have stated, i am actually surprised it took them this long to design a frog pokemon with a prominent tongue, but im glad this was how it was worked out. It fits with the motif, adds style to the design and it's clever as hell.