I have no idea how it happened, and I can't find any info online about it, but somehow, I managed to get two characters to equip the same weapon at the same time. Anybody know anything about this?

I haven't seen that one. I've seen getting stuck in a wall during a whip many times. I've seen an orb treasure-chest that opens multiple times (giving multiple orbs). Whether or not attacks hit or the damage gets queued, or how is all a big confusing mystery to me. I'm sure I've seen a bunch of other glitches over the years, SoM is certainly not the most stable of RPG engines from that era.
Ask this to people who do TAS.
Also now go abuse the results of the glitch =P
Sik wrote:
Ask this to people who do TAS.
Also now go abuse the results of the glitch =P
Want to see something truly incredible?:
https://www.youtube.com/watch?v=0TWQr0_fi80 I've also seen people glitch through walls on Doom into a strange, non-updating frame buffer void.
Doom wall glitching is actually rather common, all you need is a broken level structure, something some level editors seem very prone to cause (also two linedefs that are too close risk confusing the engine if the player crosses both in the same tick, since the engine will only notice the first cross). Also that effect you mention is usually called "hall of mirrors", basically the engine simply doesn't bother drawing the columns for which it can't find textures for (which is obviously the case when you're outside any sector).
Back on-topic, I assume both things were equipped with such timing that the game added the equipped item to one character without removing it from the other character (or the inventory, if it was there).