Grandpappy Cromdar's Whizbang Zoo! is a well-done and imaginative funhouse dungeon. It comes with its own little bestiary of completely new and interesting creatures, all lavishly illustrated by the author, David Lewis Johnson.
(I made sure that the review below contains only a minimal amount of spoilers regarding the adventure.)
The background of the dungeon is very simple but it properly establishes the mood one expects from a funhouse dungeon like this one. After numerous adventures around the world, Grandpappy Cromdar decided that, instead of building a stronghold like every sane high level fighter would, he would convert a dungeon to a family friendly zoo. Unfortunately for him, the zoo's monstrous inhabitants took over the place and now roam freely. There is rumour of great treasures lying in there, as well, so both the philanthropist and the opportunist types of characters have motivation to go there.
The product's first half details the 22 new monsters. They are statted for easy use with most D&D-esque games (HD, attacks, damage, ascending and descending AC, movement, and XP), plus each is gorgeously illustrated. Furthermore, each stat block includes the following information: how big the creature is, what it smells and sounds like, what its favourite pastime is, and what its turnoffs are. Thus we learn that a Gongwarped Fisherman sounds like a "conniving 3rd Reich pseudoscientist", its favourite activity is a "toss-up between vivisection and testing new mixtures of herbal remedies", and it really hates "being proven wrong".
The creatures are rather similar to the ones in Isle of the Unknown considering their appearance: a turkey with gorilla-arms, a kangoroo with an ape's face and insectile sword-claws, or a dog with a giraffe's neck and a ducky head. However, with the additional information provided in the stat blocks as well as the descriptions, I personally find them much more imaginative and appealing (although I understand the design choices behind Geoffrey McKinney's work), as the added details make the mental images in my head more vivid and well-rounded (in the sense that these creatures really have a character, and the referee is provided just enough to make them come to life, as opposed to being mere stats and special abilities).
The second half of the product details the actual dungeon, spanning over three levels and more than a hundred areas. The layout seems fairly good and the room descriptions are superbly done. Each numbered area has a name and a short description, and even the empty ones are given some nice detail (I think I found only three truly empty rooms). The monsters are always doing something, or their most probable reaction is given, instead. The treasure is mostly of weird or anachronistic items (e.g. pool table, portable gas forge, and silver statues of Cromdar in various fashion runway poses).
The dungeon is further divided into four zones, each with their own random encounters. These tables only determine the number and type of monster encountered; however, as each of their stat blocks provide insight into their character, it is quite easy to figure out what they might be doing.
Also, some of the areas include an appearance of Grandpappy Cromdar giving pro tips to the party. These may be easily ignored by the more serious referees - or, if embraced its craziness, could be used to further support the funhouse nature of the location.
The only thing that I dislike about the dungeon is that monster stats appear right after the monster's name in the middle of room descriptions. However, I understand that all of the room descriptions are fairly short, so taking note of what is happening in the room by a quick glance or checking the monster's stats might not take much effort in actual play.
Grandpappy Cromdar's Whizbang Zoo! is available in PDF format on both RPGNow and DriveThruRPG for merely 5 bucks. I whole-heartedly recommend it, especially for those who like funhouse dungeons, but it is probably worth its price for only the critters included.