The director reveals he had seen something special in Lovato when she auditioned for his 2003 movie Spy Kids 3-D: Game Over, and although she didn't land a role in the film, he kept the star in mind for future projects.
The perfect opportunity arose earlier this year (15), when he decided to write a part for Lovato as a guest star on the series, which features Lovato's boyfriend, Wilmer Valderrama.
He explains, "I've always been a big fan of hers and she's on tour a lot, so when she'd come to set to visit (Valderrama), I threw out that we'd love to put her in somewhere."
Rodriguez went on to praise Lovato for her "great personality" and "great acting chops", and insists he'd welcome the pop star back anytime.
He adds, "She was fantastic. She's really got a great screen presence. If there's time for her to come back in the series she can."
From Dusk Till Dawn: The Series, which is based on the 1996 movie starring George Clooney, also features Danny Trejo, Esai Morales, Jeff Fahey and Briana Evigan among the castmembers.
The second season of the show premieres in the U.S. later this month (Aug15).