Things coming together quickly now! Here's a little Dr. Lunatic themed scene for you. Pumpkins are very simple enemies, they just constantly head forward (turning if they hit a wall), walking right off ledges. They take only one hit, and are worth no points! The one that appears to be flying is actually just falling off of the Candle, which one can of course stand on like any ordinary candle.
Now why would an enemy be worth no points? Because of the Pumpkin Patch (half-hidden behind a Pumpkin)! These generate a Pumpkin every 2 seconds (alternating left and right). They'll stop generating when there are 10 Pumpkins of theirs around. As soon as you smash some, though, they start right up again to get it back up to 10. It takes 10 hits to destroy a Pumpkin Patch, and you get 200 points for it, so it's good stuff.
Of course, where there are Pumpkins, you need a Pumpkin Gate. It works just like a Bat Gate, but thankfully Pumpkins are much easier to beat without getting hit. It always bothered me how the only Gate available was for creatures that are such an incredible nuisance. It's also fun that you can be annoyed by Pumpkin Patches while trying to get one of these open.
And where there's Bouapha, you absolutely need Candles! They are worth 10 points each, unless you get them all - the last one is worth 500 points. However, like Keys and Hearts, they can be destroyed by enemies and spikes. If even one is destroyed, you can't get the bonus. So that could be used for some fun levels (and nicely, you can still pass the level without them, they are only worth points). As an added bonus, just for fun, Candles are destroyed if they hit water (can't burn in water!).
I'm at kind of a loss for what else to include that is truly based on our other games... Stockboy surely has several good choices (if tricky to implement...), but other than that, the games don't lend themselves that well to being put in this game. I thought a Moon Invader would be kind of cool, or a Killer Kiwi. Hooray for obscurity! I do have a few other things I'd like to get in, though. Not all particularly Dumb Pack style, but this is Costume Party
Dumb Pack - if adding something is going to make Costume Party better and add more potential puzzles, that matters a whole lot more than shoehorning in things from other games.