The Mobius chicken strip is "infinitely delicious" - shaped like infinity
Dipper's cards have Bill on the back
Get this on tape in case I die or whatever.
Oh hey Dipper. Hey Mabel. Hey Grunkle Stan.
Two things here. First, Soos is not afraid to call Stan "Grunkle Stan." This further backs up the theory that he could be in the Pines family. Second, Soos obviously knows that the monster is not Stan; he's just trying to cover that up.