And here we have an alien mind doing it's best to be non-threatening and ending up being off-putting and doofy.
Whatever the parasite is, at least it isn't causing buddy to go full The Thing, or even propagating from Buddy. So whatever they are isn't actively malevolent as is.
I know, right? XD
Personally, I think it's a combination of unfortunately large canines and him not realizing his attempt at being friendly is being interpreted differently (plus his behavior just being slightly...odd. Might be from the head injury....)