I have no idea if anyone else has pointed this out (sorry if it has been!), but I think I found out what the heck that squiggly line on Grunkle Stan’s tattoo is.
It’s this one right here:
Here’s the funny thing… read this excerpt from Universe Today about altocumulus clouds:
”One form of altocumulus clouds, altocumulus lenticularis, or lenticular cloud, is frequently reported as an unidentified flying object because of its shape. The approach of altocumulus clouds can sometimes be disturbing, because the cloud has a dark and somewhat frightening appearance.”
Apparently, Stan has a friggin’ thing on his shoulder that just happens to symbolize a type of cloud that ALSO just happens to often be mistaken for U.F.O’s. Aliens and U.F.O’s have been heavily hinted at by both Alex Hirsch and in the title card of the show
There probably isn’t a super strong connection there, but I was looking it up and just thought it was weird. Add it next to the fact that the rest of his tattoo (what little we can see of it) looks like a weather-vane, and I think we can conclude that it’s something to do with meteorology. Perhaps Stan once had a career in it?
Is this also connected to that funky antenna thing and the barometer that used to be on his house?
Either way, I’m pretty sure Grunkle Stan knows a thing or two about weather and/or had a job that was related to it.
Another type of altocumulus cloud is something called a "Mackerel Sky". Stan most likely belongs to an order hinted to in one of Disney’s website games called “Mystery Shack Mystery”.
The order in the game was called "The Royal Order of the Holy Mackerel". Is this a coincidence? Or is it an intentional connection?