"Mama Star" is the first segment of the seventy-fourth episode of Star vs. the Forces of Evil. It premiered on May 5, 2019 alongside "Ready, Aim, Fire", and is the first segment of the eighteenth episode in the fourth season.
Star, Marco, Janna and Tom lose their memories as they traverse amnesia-inducing waters to get back to Mewni.
After what feels like an earthquake shakes Britta's Tacos, Oskar runs into the back room to discover Star, Janna and Tom tossing garbage down the magic well. Marco is checking the mural and discovers that the first Mewman settlers where just humans that somehow got lost into the magic and ended up in Mewni. Star tells Oskar that they are dumping trash down the well to get the attention of the Millhorse to come and help them. The Millhorse rises out, but tells them to leave her alone and to stump dumping trash in the well. Star decides that she will have to go down the well herself with Marco adding that they should all go. With the help of Oskar's car, Star, Marco, Janna and Tom go down the well and force the Millhorse to pull them to Mewni rather than teleport them so that they can be together.
As they are being dragged through the magic realm, Marco begins to panic as he starts hallucinating. He then openly mutters how much he still loves Star and wishes to be close to her again. Star hears this and finds it amusing. Soon, Tom, Janna and Star begin to hallucinate and forget who they are. They spot the Millhorse and believe that she is keeping them prisoner. They decide to run her over, resulting in the Millhorse having to run until she comes across a dark puddle that she falls through. The four teens then beg to be let out and Tom accidentally blows off the entire top of the car and stays on fire.
The Millhorse directs them to the Mewni well before getting dragged under, but Star, Marco and Janna get out of their seat belts and run into the magic.Star and Marco come across a baby millhorse and decide to become its "family". Meanwhile, Janna chases a dark magic puddle and comes across dark baby millhorses that she brings back to the two. A dark adult Millhorse rises out to attack the three, but a heavily injured clean Millhorse arrives to rescue them. With no other option, the Millhorse teleports the three away.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Rider Strong as Tom Lucitor
- Abby Elliott as Janna Ordonia
- Jon Heder as Oskar Greason
- Kate Higgins as Millhorse
- This episode takes place immediately after "Jannanigans".
- Marco theorizes that the first Mewmans to land on Mewni were actually humans that came from Earth.
- Marco questioning his desires in life while hallucinating may be a callback to his dream sequence in "Red Belt".
- Tom reveals that he has a more demonic form.
- Several millhorses in the Realm of Magic is revealed to have been infected by dark magic, left behind by Moon when she was stranded in "Divide".
- Britta's Tacos is revealed to have been built over a tar pit. This would explain why there is a mine shaft like basement underneath it.
- August 9, 2019 (Southeast Asia)