The teenage stars appear together in the hit Netflix science fiction series and, over the weekend (March 28-29), Noah tagged his pals in a post that said: "Tag two people that want to hook up with each other to make things awkward."
Noah didn't elaborate on the post, and neither Millie nor Finn commented, leaving fans wondering whether he was being playful or if the pair were actually interested in a romance.
The comment comes two months after Millie, 15, confirmed her romance with the son of England Rugby World Cup legend Jason Robinson, Joseph Robinson.
The actress was believed to have met the 17-year-old in the Maldives at the end of 2019. They confirmed the relationship via Joseph's Snapchat, with a "Ly (love you) x" caption alongside the pair posing together in front of a mirror.
The stars are currently on a break from filming the fourth season of the popular show as the ongoing coronavirus pandemic brought filming in Atlanta, Georgia to a standstill earlier this month.