One Piece. The deformations of faces pushed to the limits Looney Tunes-style are probably the most prominent factor. Luffy's Gum-Gum Fruit powers are a close second, looking like something taken out of a Tex Avery cartoon. It's even been speculated that its lack of similarity to the archetypal style of anime is a factor in why it took so long to catch on outside of Japan. tvtropes.org/pmwiki/pmwiki.php/Main/Animesque
@S John,@S John