Close behind the temptation to laugh at bad monsters (ha, ha and ha) is the temptation to improve them. It's the same urge that led Neil Gaiman to write a "Prez: The Teen President" story in heroic rather than camp mode in Sandman, or Alan Moore to use Mr. Mxtyplxzwhatever as a very serious villain in one of his DC series. This upgrading from silly to serious is known in TV Tropes land as Cerebus Syndrome, after the Dave Sim comic series that evolved from a funny-animal spoof of Marvel's Conan series to something altogether more profound.
Soon to be released, if not already out, is a fine example in the D&D canon: Paizo's Misfit Monsters Redeemed. How successful have Messrs. McComb, McCreary, and Sutter been? Hard to judge from just the blurb. Some of their "misfits," like the dire corby and flail snail, I never thought were that bad to begin with. With others, like the disenchanter, I'm highly skeptical about their chances for redemption at all. And others show real inventiveness and promise, like the adherer rethought as a horrible spider-silk mutant, and the flumph as a Derlethian herald of the fight against the Great Old Ones.
Frances Ethel Gumm or pop star Stefani Germanotta, a change of name is going to be a necessary part of any serious rebranding. There's no room for a "flumph" in the Cthulhu Mythos, and I'm guessing most people hate the flail snail because of its silly rhyming name. This point was grasped by Max, of the currently inactive blog Malevolent and Benign, in his great series of Tirapheg Week posts. Five differently named variants on the classic half-baked, purposeless weirdo monster from the Fiend Folio - living statue, alien wizard, mutant mishap, limb-collecting pirate, and three-headed lounge singer - for five different game systems, all brilliantly executed.
What drives people to upgrade the classic old stinkers of monsterland? The urge is greatest, it seems, for the "failure to converge" monsters. These collections of haphazard bits, pieces and abilities form a kind of Rorschach test, an irresistible challenge to create meaning out of meaninglessness. I'm sure there are other improvements out there that I haven't come across, and it would be interesting to know of them.
Next: my own tirapheg variation.