Pokémon Sword & Shield introduced camping as a way for trainers to heal and bond with their Pokémon team. After enjoying some curry with particularly sociable Pokémon, some trainers have encountered wild Pokémon wandering into their camp and asking to join the fun.
Now, surely these wild Pokémon are just looking for a few table scraps and maybe a wack at one of those flashy Pokétoys before parting ways when the trainer breaks down camp. On the contrary, the curious onlookers have also been so inspired by trainers and their Pokémon's wholesomeness that they wished to join the team permanently -- even if that meant holding down the fort idly in one of the Boxes.
There's no sure-fire way to attract wild Pokémon to the campsite, but trainers can lay the grounds to tilt the odds in their favor.
A Wholesome Game of Chance
Some players have noted the arrival of these unexpected guests while hanging out with their sociable Pokémon after cooking and enjoying curry at the campsite. The idea seems to be that the trainer's Pokémon are in such high spirits that wild Pokémon are inspired to join the team of their own free will. This concept is one fans of the series were introduced to early on in the anime when Ash earned many of his Pokémon's affections and loyalty through virtue, rather than catching them.
Ash must be a genuinely wholesome -- and lucky -- trainer since the appearance of wild Pokémon in-game at the campsite is still left up to chance, even when a trainer's Pokémon couldn't be more social and satiated on the finest curry. Basically, if a trainer's Pokémon are being friendly and social with each other after chowing down on curry, there's a possibility that a wild Pokémon will be drawn by the virtuous atmosphere within the camp. However, there are no guarantees.
Trainers have tried camping in various areas along routes, near cities, and in the wild area to no avail. No particular location, time of day, nor any other element appears to have any sway over whether a wild Pokémon will wander upon a trainer's campsite. It seems undomesticated visitors are only drawn by the sheer inspiration of witnessing a group of happy and inclusive Pokémon with full bellies.
It has been confirmed there aren't any prerequisites, such as having an empty party slot or creating a certain class of curry to lure wild Pokémon to the campsite. Trainers have claimed sightings of wild Pokémon in their camp after simple Milcery class concoctions and with a full team.
There is a theory that some of these encounters may be tied to Currydex achievements, as some trainers have noted that wild Pokémon with curry ribbons can turn up and ask to join their party just after they're finished cooking. However, this still seems to be a pretty rare occurrence even when curry milestones are met.
Gotta Befriend 'Em All
Though we don't have a lot of specifics, it's endearing to know that camping with a party full of happily satiated and socialized Pokémon can inspire newcomers to want to join the team. The only thing this hidden mechanic is missing is a running hug animation reminiscent to each time Ash makes a new Pokémon friend on his journey.
Source: Reddit