Dwarf refers to a person with one of several varieties of a specific genetic condition called dwarfism. A dwarf has disproportion of body parts. This is generally caused by a genetic or nutritional disability. Any adult human below the height of 4'10 (147 cm) is considered a dwarf.
One Piece has a great story and does not have a lot of filler episodes.
The main risk with fillers is something called Inflammatory Granuloma - referring to the hard lumps that can form in the lips. With the new organic injections, these side effects are very rare and because the fillers are natural, every side effect is reversible because the fillers can be dissolved with an enzyme.