The pet rock is a miscellaneous quest item in Fallout 76, introduced in the Wild Appalachia update. A medium-sized rock with a white smiley face drawn on it. It can be found in Camp Adams, northwest of the campfire, during the Ronnie McAdams version of Campfire Tales.
Pet Rock, Wasteland Wiki
Johnson's Acre - Independent Fallout Wiki
Heart of the Enemy - Independent Fallout Wiki
Campfire Tales, Fallout Wiki
How to Care for Your Pet Rock (with Pictures) - wikiHow
How to Care for Your Pet Rock (with Pictures) - wikiHow
Carleton Mine - Independent Fallout Wiki
Fallout 76 PC Pet Rock Legacy Item Collectibles Super Rare FO76
The Elusive Crane, Fallout Wiki