Martha shares a couple of choice similes: "dry as a contribution box" and "plump as a partridge." This is part of a complete episode.
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The current cartoon at xkcd is inspired by the simile as neglected as the nine button on the microwave. Discussion in their forums reveals that I'm far from the only person to use settings like 0:99 to heat things up.
XKCD is one of my favorite cartoon sites.
One of my favorite similes is: Her grammar was as careless as, well, like, you know ... whatever.
Ha! When I saw the title of this thread I immediately thought of this one:
Heimhenge, even before reading Gödel, Escher, Bach I enjoyed self-referential humor like your grammar simile. Most people enthuse over the Austin Powers movies more than I, but even I laughed aloud at "He has a certain quality, a certain...I don't know what."