This is partially about David Addison the character, but slightly more about Bruce Willis the actor in a way.
We've all commented on how well Bruce did in the dance sequences, and those of us who have seen the DVDs, will have seen Bruce joked about how he removed the bit on his resume which said he was "an actor who moves well" after doing the dance sequence.
If you watch the way Bruce moves in ML, the way he moves is almost like a dance, his timing and movement are always spot on. He is excellent at physical comedy too. Even when he is ducking from something that has thrown at him, or just leaving Maddie's office, he is dancing all the way. He knows when movement is needed, and when to be incredibly still. It is never overplayed, and doesn't descend into farce or becomes too cartoon-like either.
I wanted to post this, because it's just soo darn impressive and the more I watch him, the more impressive it is to me.
"You can lead a horse to water, but that doesn't make it a duck"