By Natalie Abrams
December 02, 2014 at 12:00 PM EST
Diyah Pera/The CW

Warning: This story contains major spoilers from both The Flash and Arrow. Read at your own risk.

Looks like the Queen family might be expanding for once.

During the first hour of the epic two-night Flash-Arrow crossover event, Oliver Queen (Stephen Amell) ran into a very familiar face (Anna Hopkins), whom Arrow fans may remember first appeared in a season 2 flashback as one of Oliver’s trysts who ended up pregnant. The late Moira (Susanna Thompson) paid her to disappear and lie about losing the baby, so Ollie was none the wiser.

While it’s not explicitly stated that Oliver is a father—though it was pretty darn obvious on The FlashEW can confirm he is the daddy. “Ever since [episode] 220, the idea that Oliver may have had a kid—and now we’re finally confirming it—is something that I put under the same category of Felicity’s backstory,” executive producer Marc Guggenheim explains. “We have ideas and we know what we’re going to do, we don’t necessarily know when we’re going to do it.”

It sounds like fans won’t have to wait too long to find out more about the mystery girl—she still has no name, though Green Arrow fans have speculated that she’s Sandra Hawke. “The person who we see in the Flash-Arrow episode will make another appearance on the show this season, but we’re not sure if it’s going to be on Flash or Arrow,” executive producer Andrew Kreisberg says. “That’s definitely something we’re going to be picking up on.”

The big question now is when Oliver will actually learn the truth. “I don’t know that Oliver necessarily will be the first one to find out that this little person exists,” Amell teases.

Arrow airs Wednesdays at 8 p.m. ET on The CW.