Moon and River were good friends when they were kids. They are one of the only married couples in the series. They have a daughter, Star.
- In "Royal Pain", River admits that he may have been inconsiderate and that was probably why Moon threw him out of the castle. He promises Star that he'll patch things up.
- In "Storm the Castle", Moon tells River that she loves him.
- "Game of Flags" shows that Moon married River despite her family not approving.
- In "Deep Trouble #2: Ole Moon River", young River (with the advice of Star) makes various attempts to make Moon fall for him. He later saves Moon's life by knocking out Dirt, who was trying to murder her.
- In "Face the Music", River is very worried about Moon going into the Forest of Certain Death alone. She reassures him, saying that she can handle it and kisses him.
- "Star and Marco's Guide to Mastering Every Dimension" reveals that Moon and River met on the battlefield after the Johansen clan was summoned to help fight a monster attack.
- In "Return to Mewni". River packs Moon corn with a note saying I corn't wait to see you again and a fan that has a picture of him blowing her a kiss and says Miss You!! Kisses OXOX River (your husband).
- In "Moon the Undaunted", River believed that Moon could make important decisions for herself. He later gives her an apology meat but she tells him that what he said was a relief and thanks him. He blushes, shoots finger guns and tells her Hey! Anytime pal! River then walks off wondering if he actually called the queen pal.
- In "Moon the Undaunted', River runs up to Moon and congratulates her on defeating Toffee. She hugs and thanks him.
- In "Marco and the King", it reveals that River calls his wife Moon Pie.
- In "Marco and the King", River misses Moon after waking up in the morning. He later admits to Marco that the reason he keeps on partying is that he's worried sick about Star and Moon. He begins to cry, thinking they weren't coming back.
- In "Puddle Defender", Moon exclaims that she's deathly worried about her husband.
- In "Toffee", after returning to Mewni River wonders where Moon Pie is.