The Flash half of the December 2015 Flash/ Arrow crossover on Tuesday introduced new-to-TV DC characters—and in Wednesday’s Arrow half we received tips on new plot lines for both the shows—as well as a nod to Legends of Tomorrow, set to launch on the CW in 2016.

Here’s some likely plot-crackers we’ll be learning more about down the road.

The Flash seeing double?

The Flash sees a "ghost" of himself, on the CW show "Arrow."

Flash fans know that when he sees a “ghost” of himself running nearby, there’s a time travel adventure coming soon.

Oliver had a feeling about this kid.

Oliver plays with a boy he has learned is his son, on the CW show "Arrow."

Turns out, it’s a boy! The Arrow has a son.

The Flash outruns a blast of energy from Vandal Savage's magic staff, on the CW show "Arrow."

Now we know why Barry time traveled. Vandal Savage destroys Central City with his magic staff—we even see Oliver get ashed. However, Flash outruns the blast, ending up a day back in the past.

Barry tries unsuccessfully to argue against changing the future, on the CW show "Arrow."

Oliver convinces Barry changing the future is a good idea. Barry warns him time travel always comes with bad consequences (like tearing holes in the fabric of the universe bad) but Barry gives in, and they upgrade their attack plans accordingly.

Vandal Savage, reduced to ashes during battle with Arrow and The Flash, on the CW show "Arrow."

This time around, the boys blow up Savage! (That’s him, the pile of dirt on the floor).

But does the aforementioned time traveling mess anything up? Everything seems OK as the show ends with a warm Oliver/ Felicity cuddle.

Oliver and Felicity cuddle, on the CW show "Arrow."
Malcolm Merlyn, collecting Vandal Savage’s ashes, on the CW show "Arrow."

…and Malcolm Merlyn collecting Vandal Savage’s ashes—a good hint he’ll be back for DC’s Legends of Tomorrow, slated to premiere on January 21, 2016.

Photos via Arrow (CW)