A couple of figures of speech usually - probably justly - overlooked are Wellerisms and Swifties.
Wellerisms are named after a Dickens character who liked saying things like, "'Out with it!' As the father told his son who'd swallowed a farthing." I believe Lincoln used a lot of Wellerisms, too, although they wouldn't have been called that at the time. I have an impression he was known to make mildly off-color remarks with the tagline, "As the widow said to the preacher."
Another is the redoubtable Tom Swifty. The traditional one is an adverbial pun - "Is that bear still outside?" he asked intently. - but I have a fondness for variations. "I have multiple personalities," Tom said, being frank. or "Thar she blows!" Tom wailed.
It would be a fun, but stupid, idea to have a single character in a book who spoke either in Tom Swifties or Wellerisms. Maybe a combination of the two?
"'It's over my head,' as Cleopatra remarked falling out of the boat, deep in denial," or "You'll just have to stick it out a little longer,' as the urologist predicted peevishly." "'I have nothing to hide,' as the eunuch barely disclosed at the nudist colony."
As I said there's a reason these figures of speech are overlooked.