Venomoth and Venonat were encountered at Vermilion Forest. Go caught Venomoth after spotting it flying through the air. Venonat was found sleeping in a tree, but Go's attempt to catch it failed when Venonat broke out of his Poké Ball. With Scorbunny's help, Go battled Venonat and managed to catch it.
None of Venomoth's moves are known.
Venonat's only known move is Poison Powder.
Butterfree was encountered at Vermilion Forest. He was found resting on a large tree, which Go climbed with Ash's help. When Go accidentally dropped his Poké Ball, Butterfree attempted to flee, but was caught when Scorbunny kicked the Poké Ball at him.
In SS015, Butterfree was among the Pokémon that Go used to help find a Cubone's bone. Once they found the Mankey that stole it, Butterfree helped attack it.
Pinsir was encountered at Vermilion Forest. It attacked Ash and Pikachu, trapping them in a ring of large stones. It then went after Go, who threw random objects in an attempt to defend himself, eventually accidentally throwing a Poké Ball and catching it.
Beedrill was encountered at Vermilion Forest. It was part of a swarm of Beedrill that attacked Go when he caught Kakuna. When the others were trapped by Pikachu's Electroweb, Go caught the lone Beedrill that wasn't hit, assuming it was the strongest.
Scyther was encountered at Vermilion Forest. It easily repelled Go's Poké Ball and sent him and Scorbunny flying. Go later encountered Scyther again, this time using Scorbunny to battle it first. Together, Go and Scorbunny weakened Scyther enough for Go to successfully capture it.
Dewgong was caught by Go to carry him and Ash across the sea while trying to find the Dragonite Island. However, along the way, it saw another Dewgong and fell in love with it, inadvertently chasing it into a storm, where Ash and Go fell off of its back. It later reunited with them at the island, having failed to find the other Dewgong.
In SS015, Dewgong was used by Go to explore a pond in order to find a bone belonging to Cubone. After a while, it was able to retrieve the bone and return it to Cubone.
Cubone was encountered at a park in Vermilion City. After witnessing Cubone have its bone stolen by a trio of Mankey, Go agreed to help retrieve its lost item. With the help of his Pokémon and Ash, Go was able to reunite Cubone with its bone. Afterwards, Cubone decided to join Go's team and allowed itself to be caught by him.
Whilst walking to the Vermilion Gym with Ash, Go and Raboot spotted Spearow flying past, causing Go to chase after it. Go later arrived at the Gym where he revealed to Ash that he was successful in catching it.