So! They're thumtacks/pins and string! Putting together amature deductions, connecting dots that don't always lead to the right conclusion.
This above is the generic version! Then we have some "special versions" that can appear in the overworld as NPC mostly, but if you encounter three Snoopins at once they look like this (same stats, maybe different dialouge/flavortext).
(Inspired by the Detective Boys from Detective Conan; Ayumi, Genta and Mitsuhiko)
(In addition to the more obvious pun of snooping and pin, a Danish word for string is "snor", making the "Sno" at the beginning a reference/pun too!)