Daniel Redstone's eyes take on a twinkle, and the skin around them starts to crinkle, when his ironic wit comes into play - just like my dad's.
Another, more recent persona that has contributed to that particular character has the same feature - one of the major reasons I admire his creator, and use the persona to help create a more vivid image.
Daniel also has a hard time waking up each morning. He probably got that from me, but his dry verbal wit also comes from my father.
One important thing - once a quirk is established, it has to be consistent - to the point that, when the narrator mentions it, you identify the character right away.
Ann