Rihanna and A$AP Rocky had slime on the brain for their son RZA‘s birthday.

Indeed, the couple celebrated the 4-year-old’s special day at the Sloomoo Institute, a slime museum, in New York City May 13, alongside family and friends.

Rihanna and A$AP—who are also parents to son Riot, 2, and daughter Rocki, 8 months—went all out for their eldest kid’s birthday, renting out the entire venue for the celebration, per People.

For the “immersive” soirée, party guests enjoyed sensory play activities, interactive installations and custom slime creations while being surrounded by “over-the-top balloon decor,” according to a rep from the establishment. But that wasn’t all. Indeed, party guests got to experience the museum’s signature “Sloomoo Falls,” in which attendees get doused in slime. 

And, Rihanna, 38, of course joined in on the fun. After all, the “Love on the Brain” singer participated in the venue’s iconic experience and was drenched in gallons of goo as she stood under the slime waterfall, according to the Sloomoo Institute rep.