We need a new Psyduck! New viewers will never know how humorous he was.
I think Oshawott is the closest we've had to a new Psyduck. He comes out of Ash's pokeball without permission, to take the role of another pokemon in battle. Although he can be comic relief in battle, it's not quite the same. Part of the psyduck gag was that his trainer got frustrated at him, and that he acted very stupidly. Neither Oshawott, Piplup, nor Gible's comic relief has filled this well.