Guys WHAT IS THIS? (Melissa in costume in Riverdale)

1) Melissa was probably filming near their set, that day, and decided to pay a visit.

or

2) They could have been all together, filming some kind of CW promo.

I really don't think a legit Supergirl/Riverdale crossover is in the cards, lol.

Lol I don't watch Riverdale (almost typed Rivendell because I'm more familiar with that xD) but I do know it's not the same universe as DC. But the shot is funny though. Either it's a joke, or the way I can guess, within the universe Supergirl is a TV show like in real life, and Melissa Benoist played herself for a cameo

2) They could have been all together, filming some kind of CW promo.

I would lean towards that option myself.

Supergirl's studio is shared with Riverdale and Melissa is good friends with Lily Reinhart. She was stopping by to say hi during a break on both shows. The director of Riverdale took a picture of them together through the camera on set. It was misleading, in my opinion to take the photo through the camera lens, implying a crossover. So far, no crossover is planned. just two friends visiting

Lolz k

To mix Supergirl and Riverdale would be so against comic book cannon I'm not sure Warner Brothers would allow it. I have a feeling the next blond female to visit Riverdale will be an actual Acrhie comic character, Sabrina Spellman aka Sabrina the teenage witch. Cue Melissa Joan Hart camio as one of Sabrina's aunts.