Reply #11: I'm partial to the pulsating cactus full of deadly spiders.

[Denninmi]

Since I worked at a garden center for about 20 years from the mid/late 80s to the mid/late 00's, I actually got to hear this one from a couple of customers -- it was always someone they knew or knew of, who had bought a large cactus somewhere (usually when traveling to the SW), brought it home, and one day, it began to pulsate or "breath" -- next thing they knew, it ruptured and all kinds of giant, deadly spiders ran out.

Biologically impossible, as Snopes points out. What amazed me was that people believed this -- I had one pretty regular customer that wanted no part of cactus or anything else with a large, fleshy stem or trunk that could "hide spiders".

http://www.snopes.com/horrors/insects/cactus.asp

As a corollary to this one, I was always amused at the number of people who would buy a plant, or be given a plant, and then call us all freaked out because there were "bug eggs" or "snail eggs" in the soil -- they were fine after I told them (which got old after a couple of hundred times) that it was just Osmocote time-release fertilizer pellets.