Pascal is a sea otter you can encounter in the latest summer update for Animal Crossing: New Horizons. You can only meet him if you obtain scallops, which you can find from diving into the ocean and finding scallops. The scallops are a random item you can find while swimming throughout the ocean, so you may need to spend a bit of time searching in the ocean. Make sure to dive down whenever you see bubbles coming up from the water.
Once you find a scallop, Pascal shows up immediately. He pops up nearby and asks if you’d like to part with it. If you’re willing to do so, he will offer to give you a mermaid item in return. The exchange is pretty fast, but he has a lot of dialogue. After he finishes speaking to you and swims away, you will have new mermaid items in your inventory, and the scallop will be gone.
He won’t do this for you every day. Pascal will only show up at least once a day, so he won’t consistently speak to you each time. Pascal may not show up on your first scallop discovery, but if he hasn’t visited you that day, you can keep looking around for them. He only does it once a day, giving you a chance to earn new mermaid pieces once a day. You can choose to time travel to obtain more mermaid-themed items if you want to have more of them sooner.