no there isn,t
but there should be
No, 'thingy' is not even a word, it's slang.
A blob thingy?
Habius corpus
a sentence is a long word thingy
The thingy you speak of is profoundly called a What-Cha-Cha-Macallat and you put there special brand of fajita sauce on it.
a thingy
what's cm and adjust the bar thingy what's cm and adjust the bar thingy
The word lantern comes from greek word Lant(Glowing) and Ternus(Thingy)
a word describing a thing that you momentarily forgot the name of
Look at that Elf thingy Dancing......
Theres this thingy, called a repair shop. This thingy also known as an autobody will fix your problem.
The word thingy is used informally, so grammatical rules pursuant to its usage are rather poorly established, but I would say that the logical plural would be thingies.