Before he left in early December for St. Jude Children’s Research Hospital in Memphis to have surgery on a cancerous brain tumor, 5-year-old Wyatt Haas of Fallon, Mont., had his dream fulfilled. Wyatt got to ride on a unicorn.

Two of the mythical creatures, in fact, appeared at a last-minute party in a park thrown by Wyatt’s kindergarten class. Two of the children’s mothers who own horses painted their animals the colors of the rainbow with bright chalk sticks; other parents brought party favors, two cakes and juice. Afterward, Wyatt asked his mom to take him to a unicorn store.

“I think the whole thing blew his mind,” Corissa Haas said. The family is hoping to cover Wyatt’s medical expenses with a GoFundMe account that has raised more than $8,000.