Mermando

Mermando becomes Mabel's boyfriend in the episode "The Deep End." But Mabel helps Mermando get back into the ocean to return to his family.

Mermando's story
Mabel wanted to know how Mermando lost his family and friends, so he explains. He was swimming with his friends until he was caught by a net from a boat. The boat took him to a bait shop to kill him. Before the people in the boat took him into the shop, he jumped out from the back of the car and escaped. And he ended up in the Gravity Falls pool.

Mabel and Mermando's kiss
At the beginning of the episode, Mabel tried to kiss Mermando, but he asks what she was doing with her mouth, and to make an excuse, she said that she was eating a sour candy. Mermando asked for a candy, and after complete silence, Mabel said no.

On the last part of the episode when Mabel and Dipper return Mermando to the ocean to see his family again, Mermando kisses Mabel before they say goodbye.

After Mermando left, Mabel was lonely, sitting in the pool. She recieved a message in a bottle from Mermando saying, "Dear Mabel, I am home with my family, and I am very happy. Our first kiss will always hold a place in my heart. Technically hearts...As a merman I have, like, 17 hearts. Horrifying but true! *More bottles on the way!"