Yes, a total blackout was caused by those little squishes.
Where? The Philippines
How? A group of jellyfish clogged up the pipes in the Sual Power Station. The locals at the time thought it was a bug or glitch, but in fact it was about 50 truckloads of jellyfish that were sucked into the sea water intake of the power station on the island of Luzon.
Learn Something Fun: Medusa (plural medusae) is another word for jellyfish. Medusa is also the word for jellyfish in: Greek, Finnish, Portuguese, Romanian, Hebrew, Serbian, Croatian, Spanish, French, Italian, Hungarian, Polish, Czech, Slovak, Russian and Bulgarian.