Gwen Stefani's son, Apollo, had a very special birthday party over the weekend. In fact, it seems his mom had just as much fun as he did! The Scooby Doo-themed festivities included Blake Shelton dressing up as Shaggy and Stefani embodying Daphne.

Always a good sport, Shelton put on an impressively messy wig for his portrayal of the Scooby character. His pop-star girlfriend sported a bright pink wig that looked like a natural fit for her youngest son's 4th birthday celebration.

Shelton has been getting close to Stefani's three sons. They're often out roaming the land on the country star's Oklahoma ranch, and he even taught her oldest son, 11-year-old Kingston, how to go mudding in a truck. Stefani previously told Marie Claire that Shelton's ranch is the perfect spot for her sons. "We cook and get muddy and dirty. There are ATVs. Being a mother of three boys, it’s kind of the perfect place," she says.

When the couple aren't living a country life away from L.A. lights, they're on the road surprising each other at one another's concerts. Stefani recently joined Shelton on stage at his new venue, Ole Red, in Tishomingo, Okla., then surprised fans at a concert at St. Louis Scottrade Center on Saturday night (Feb. 24).

Shelton will soon return to his big red The Voice chair — the show's new season premieres on Monday (Feb. 26).

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