The pop stars secretly flew to Seoul, South Korea, in late 2024, when they sang alongside K-pop idols for a TV show.
"A Spice Girls reunion is a way off," a source told The Sun newspaper.
"So having Emma and Mel back on stage singing a Spice Girls song together might be the closest fans get to a comeback, even though it will be with K-pop stars rather than Geri Horner, Melanie C and Victoria Beckham.
"They flew to South Korea at the end of last year and were on set for quite a few days as they battled it out with other pop veterans.
"With them alone on board, it is a big show. But there's also Boy George and loads of other chart-topping stars, which will be enough to encourage people to tune in."
The reality show will air on Apple TV and will also feature the likes of Megan Thee Stallion and Psy, the Gangnam Style singer.
Meanwhile, Mel B recently revealed she's ready to "start planning" a Spice Girls reunion.
The 51-year-old singer would love to reunite with her bandmates to mark the 30th anniversary of Wannabe, the group's 1996 hit single.
"There has to be something befitting of 30 years since Wannabe," she told Rebecca Judd on Apple Music 1.
"Once a Spice Girl, always a Spice Girl. We all feel like that, but we now are getting together because we know if we're going to do anything, we have to start planning things to get things right.
"We have to start making the plans right now and putting them into action. So fingers crossed."
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