'Supergirl' season 2 spoilers: More Mon-El–Kara moments, musical crossover with 'The Flash' coming in 2017

What secret is Earth's Daxamite visitor harboring, and how grave is it that he's now being hunted down by some unidentified space farers? Could Mon-El (Chris Wood) be the true prince of Daxam?

This seems to be the consensus among fans of The CW's superhero series, "Supergirl." One of Entertainment Weekly's spoiler room articles reported that executive producer Andrew Kreisberg teased that Kara (Melissa Benoist) may not have a very favorable reaction should Mon-El's secret be revealed.

"Secrets are never healthy in a relationship and obviously, Mon-El is holding onto something" Kreisberg said, further adding that this would definitely be something that affects Kara and Mon-El's budding relationship in a major way. He, however, refused to comment on rumors about Mon-El being the Daxamite prince.

In an earlier interview with Entertainment Weekly, Kreisberg teased that the next episode of "Supergirl" will be playing on the consequences of the kiss Kara and Mon-El shared in the midseason finale when the latter thought he was about to die, and of which they have both pretended not to remember.

"They're both obviously playing coy about what happened, neither admitting that they actually did kiss, so how and when that comes out is going to be fun and delicious," Kreisberg added.

The back half of season 2 will also be featuring the much-awaited two-part musical crossover between "Supergirl" and "The Flash. In this year's Television Critics Association (TCA) press tour, the network confirmed that the crossover will indeed be happening in the back half of the season and may potentially use mostly existing songs along with a few originals.

As to the reason why everybody's suddenly exercising those musical pipes? The CW teased that it may all be in a character's mind. Back in September, Arrow-verse executive producer Greg Berlanti revealed that work on the musical episodes began right after they finished writing the scripts for the four-way superhero crossover. They have cleared some music, drafted a few original songs, and have struck deals with music writers that he's "incredibly excited to work with."

"Supergirl" returns on Monday, Jan. 16, at 8 p.m. EST on The CW.