One of the lasting contributions of Star Trek: The Motion Picture is the now standard appearance of the Klingons, which changed dramatically from The Original Series:
However, those Klingons only appeared very briefly at the beginning of the film, saying and doing very little — they were destroyed within minutes by V'Ger.
In Star Trek III: The Search for Spock, we see a lot more of the new Klingons, in particular Commander Kruge, played by Christopher Lloyd:
In Kruge, Lloyd crafts a far more fearsome presence that his Original Series Klingon predecessors, and takes actions and exhibits traits that they did not. In particular, he shows a readiness to die while wrestling with a slimy swamp creature, just to test his own mettle.
Basically, Lloyd's Kruge is far closer in spirit to the TNG-style "warriors" than to the TOS Klingons.
How did these character traits come to be? Did Christopher Lloyd have a hand in it, or was the re-imagining of the typical Klingon officer something that was dreamt up prior to his casting?