Variety previously reported that Victoria Beckham, Mel B, Mel C, Geri Horner and Bunton would voice their likeness in a film with the "girl power" message.
Asked on ITV show This Morning whether plans were in place for an animated superhero film "with feminism at its core", Bunton replied: "That's something we are talking about."
The singer - Baby Spice - was coy about other reunion plans, only saying: "There is definitely something in the pipeline."
Mel B has previously suggested a tour but Bunton said of the prospect: "I'm not sure. I think a few shows would be great."
She said of Glastonbury, which returns in 2019, "we haven't been asked but that would be nice" and added of singer-turned-fashion-designer Beckham: "I'm sure she'll be involved in some way."
The radio host and singer said of her own plans: "I'm back in the studio having fun with some music on my own."