↓ Transcript
Panel 1:
Bink: I'm bored. Lisa's locked her new clothes away, and WoW dailies are still as dull as a doornail.
Chloe: Dead as a doornail.
Panel 2:
Bink: Huh? No, dailies aren't dead. They're dull.
Chloe: But that's not the saying. It's "dead as a doornail."
Panel 3:
Chloe: A doornail is actually quite sharp, so you're saying that dailies aren't dull at all. Doornails, are, however, devoid of life, hence the original saying.
Panel 4:
Chloe: Do you understand now?
Bink: (walking away, paws in the air) Oh just make like a tree and get out of here!