Accidental Innuendo: And Rare already crammed their usual heaping helping of deliberate adult humor into the game! There are quite a few things that are innocent enough in the normal game, but become very risqué due to the player character being of the opposite gender during Challenge 21. To elaborate: when playing through the normal game, you play as Cooper, a male who appears to attract the sexual attention of multiple female foes in the game. When you play through a second time in Challenge 21, you play as Amber, a female, who still attracts the same female baddies. The female vampires that pull you into their coffins and shut the door while hearts rise out of the casket and you slowly lose health suddenly take on a whole new meaning.
Amber's pre-boss Ghoulie self still wants a kiss from her non-Ghoulie self...
Perhaps worse is the second mummy you meet in the game, who startles you by jumping out of a large vase, triggering a Super Scary Shock. The camera shows him, then cuts to the player, then cuts to him doing menacing pelvic thrusts. Poor, poor Amber...
The fact that the next shot is of the player character leaping into the air with an exponentially more shocked expression than before doesn't help.
Freud Was Right: Play this game long enough, and pretty soon you begin to believe that EVERYTHING Fiddlesworth says is innuendo ... although it's possible that Rare did this intentionally - almost everything he says does actually have a potential double-meaning. Knowing Rare, this isn't Accidental Innuendo either...
Fridge Logic: Babs Buffbrass, the janitor, gives you a gun that fires soda-pop cans, making a horrible mess that she detests cleaning up, and orders you to place it in the trash. She then immediately gives you detailed instructions on how to use it to make the very mess she hates, even though all she wants you to do is to throw it away. She is then confused as to why you used it to defend yourself when she reclaims it from you...
There's also the Baron, who literally hands you the means to defeat him with full knowledge that that is what he is doing.
Baron Von Ghoul: I'm a sporting gentleman, so take this weapon. It'll give you a fighting chance!
The Baron also gives you the tools to soundly defeat his Ghoulie minions, if it is true that he was disguised as Crivens the butler through the whole game.
Goddamned Bats: Imps of any sort, mostly the basic and ninja varieties. While normal Imps go down with only two swift attacks (or one swing of any weapon), many challenges instruct you not to kill any Imps while whaling on other enemies. Since Imps only have 5 HP each and will easily disappear in a crowd of taller baddies, it's incredibly easy to accidentally dispatch one and summon the Reaper in the middle of plowing through a mob of enemies.
Skeletons get this way during fights involving larger, tougher enemies than them. They will attack in swarms, frequently holding (or quickly acquiring) weapons that can take off a significant chunk of your Hit Points, and it's often a choice between whether to stave off the bigger baddies' probably-lethal attacks or the equally dangerous onslaught of Skeletons - there isn't necessarily enough time to avoid both.
Narm: Many parts of the game that might have been scarier in a different, less cartoonish context. But it's entirely acceptable seeing as the whole game is intended to be one big Parody of the Haunted House genre anyway (and thus not meant to be serious or scary).
Nightmare Fuel: Some of the enemies, particularly Jessie & Clyde (two separate beings sewn together into one enemy ... * shudder* ).
Looking at some scenes in the house leads to some pretty disturbing mental images of what might have happened shortly before Cooper got there. Of note is a side hallway in the Infirmary area, which is mostly obstructed by a cabinet and is filled with overturned hospital beds and ultimately dead-ends at a hastily boarded-up door ...
Those poor other kids trapped by the Baron! If you don't rescue them from their Bound and Gagged situations (which are already pretty gruesome, with them being stuffed in freezers, strung up by their ankles, set on top of a bed of hot coals, and served for dinner, among other things) before the 13-minute timer in the final challenge is up, they'll be trapped in the house FOREVER!
Close examination of Zombie Pirates reveals that they are missing large chunks of flesh and muscle, as well as the right half of their mouths, permanently exposing their rotting teeth and gums. The holes in their skin appear to be dark and rotting around the edges... Granted they're obviously supposed to be decomposing since they're dead, but still, for an E-rated game, they're pretty darn hideous.
The first corridor features the stuffed and mounted heads of Banjo AND Kazooie. I grew up on them, and they just look really wrong here, not to mention how they got stuffed and mounted in the first place.
That One Boss: Ghoulie Amber is pretty dang tough without use of the Turbo Cooper power-up. Even then, it still requires near-pinpoint accuracy as to when you attack, or else you'll swing too early and won't be able to dodge her attack that immediately follows, or you'll swing too late and your attack won't connect before she whomps you.