The Clumsy Coasters are silicone coasters designed to look like spilled, clear fluid. The idea is you put a drink on top of them, and they give the appearance that either the contents have spilled, or the condensation on the glass has puddled. If you have a fastidious aunt with limited eyesight and an antique wood table, the effect will send her into cardiac arrest. (Which, depending on your relationship with her, may or may not be what you want.)
I tried these on a number of surfaces: Corian (tm), granite, wood. Maybe it's all in the eye of the beholder, but I felt more like I appreciated the idea of the joke rather than the joke itself. But if I hadn't known they were fake, I suppose I might have had a moment of "uh oh" in the same way a whoopie cushion produces just a moment of "is that REALLY what I THINK it is?"
The main drawback is the size. They are really designed for mixed drink size glasses, or the bottom of a wine or martini glass. A tumbler's circumference was such that the glass bottom always overlapped the coaster. It ruined the effect of the "spill." It looked okay with a 12 oz can.
Do they work as coasters? Well, the silicone won't let fluid through, but the design is such that if you live in a climate that is very humid and use these for iced drinks, the condensate could easily flow off the coaster onto the table. (Don't let your aunt see that!) These coasters should be fine, however, for hot drinks.
They are cute in the way whoopie cushions or Groucho glasses are cute, and would be nice for low-level gifting such as office parties. Recipients will smile and appreciate the gesture and may use them for a quick laugh with guests.