Harper and Sarah are identical to their sister Lana appearing to be like mini versions of her. To differ both sisters, Harper wears a Shellder shirt and Sarah wears a Slowpoke shirt. Both wear small yellow headbands on their heads. Harper has three hairy tips while Sarah has only two.
When they meet a new Pokémon, they become very curious and excited often getting carried away in what their doing but they can be very helpful when they want to be. They are often shown to be very hyper children with a great love for Pokémon. They sometimes have a habit of unintentionally embarrassing their older sister Lana.
Season 20: Sun and Moon
In Yo, Ho, Ho! Go, Popplio!, Harper and Sarah greeted their older sister and Ash when they come to visit Lana's home. They immediately took a liking to Ash's Pikachu and brings it to their room. The twins then start to pull on Pikachu's face much to his dislike. Harper and Sarah then ask Lana if Ash is her boyfriend, causing her to quickly deny it. Pikachu then start to get uncomfortable with the twins and used Thunderbolt on everybody.
Then, they make a reappearance in Getting the Band Back Together!, watching a concert performed by DigDugLeo on television with their sister Lana.
Harper and Sarah also come to the open house at the Pokémon School in Alolan Open House!, where they get so excited about seeing all new Pokémon at the school and get a little carried away. Until, they were carried away by their mother.
When Lana switches her Popplio with Kiawe's Turtonator in The Ol' Raise and Switch!, the twins become amazed at Turtonator's size and Lana tells them to be nice to the Blast Turtle Pokémon which they agree too. Sometime later, they are seen jumping on Turtonator's back and their sister warns them not to touch it's spikes but they do causing them to explode and the twins take it as a fun surprise. Harper and Sarah also help Lana with brushing Turtonator's back.