I have two allied Pilferrets+ that are circling around me a bit, holding their arms up as if they carried a food, but with nothing up there.
#Allied Pilferret running around carrying "nothing" food
bright cedar
mossy sandal
I've seen this a couple times as well, thought it was some behaviour 
bright cedar
"Praise be to our bestest of friends" [proceeds to circle around in ritual fashion]
bright cedar
So, I think I found out what it is - the "nothing" that it's carrying is actually a stone, it's ready to throw and will return to normal animation and behaviour once it throws