In Pokemon Let’s GO Pikachu/Eevee, trainers have the option to bring out another Pokemon with them on their adventure in the Kanto region.
Depending on what the Pokemon is, your trainer and Partner Pokemon (Pikachu or Eevee) could ride that Pokemon. But riding certain Pokemon is pretty cool in Pokemon Let’s GO Pikachu/Eevee.
Check out the screenshots below:
Riding Kangaskhan (look at Eevee!)
Sorry.. you couldn’t ride Alolan Exeggutor.