So we're going back to the dungeon this time and it looks like we're doing level 3. A roll of 18 on the chart reveals our encounter is with... TARANTELLA!
That's right! A troupe of italian folk dancers spring out of an alcove and...
April Fools!
Not that tarantella, no I'm referring to the horrid pun in Moldvay that is the tarantella. (Get it? 'Cuz it sounds like 'Tarantula'? Oh my sides.)
Despite the whimsical nature of the creature's creation, this can be a pretty challenging encounter.
It says 1d3 appearing. Rolling a 5 on a d6 gives us 3 of the critters.
So three giant spiders attack a party of let's say four 3rd level PCs. Now, unlike other giant spiders, the tarantella's venom is not directly lethal (though a save vs. poison is still required). Instead, it causes "painful spasms which resemble a frantic dance." This gives the victim a -4 to attacks and foes gain a +4 to hit. The spiders have 4HD apiece, so they're hitting relatively often vs. a party that probably doesn't have much in the way of magical protection yet (THACO 16). Further, they have AC5 and enough hit points (15-20 on average) that they can withstand some damage before getting killed.
So the nutty(er) part about the tarantella's attack is that the dance has a "magical effect" and anyone seeing the victim dancing must save (vs Spells this time) or start dancing themselves! This means one hit and failed initial save could lead to the entire party succumbing to the effects on the following round. Victims will eventually (5 turns) collapse exhausted (defenseless). Where I assume the spiders can go about enjoying their meal(s).
Now, a couple notes, some to do with rules details, some more personal interpretation. First off, those fighting the spiders will need not only save vs poison every time they are hit, but vs spells every time a comrade starts to cha-cha, At least vs the initial victim of a bite. Truly harsh DMs could make PCs save not only against seeing the bitten PC's dance, but against each new "infected" dancer's gyrations. Given that 3rd level PCs are failing such saves at least half the time, this doesn't bode too well for them.
Next. Remember that each bite also deals 1d8 plain old damage. Even if the spiders don't leave the "dance party" alone to exhaust themselves, they are getting +4 to hit on those who are dancing. It wouldn't take long to just kill the PCs that way either.
Neutralize Poison and Dispel Magic will stop the beat, but that's usually beyond the ability of 3rd level PCs. I would also question (and this is one of those interpretations I mentioned) whether an infected MU or cleric could even cast a spell while dancing. That may make such a fight too dangerous for a random encounter by some standards.
So. On to the encounter itself. This could be a simple as the PCs disturbing a nest of these horrid arachnids and paying the price. For a little more fun, what if said spiders were not just looking for a meal? What if they were charmed watchdogs? They bite interlopers, let them dance themselves to the point of collapse, and then haul them back to... who? Or maybe they are the pets of some tribe of humanoids who have an immunity. Once the PCs are exhausted. The owners come out, loot them and dump them in a hole or leave them naked in the dungeon to be killed by some other nasty random encounter.