Supergirl is set to meet The Flash in "Supergirl" season 1 episode 18.

"Supergirl" season 1 episode 18 is entitled "Worlds Finest." According to Spoilers Guide, Kara meets a new ally in the form of The Flash. As per the publication, the speedster suddenly comes from an alternate universe and helps the titular heroine fight Siobhan, who is also known as Silver Banshee. Kara also develops her dynamics with Livewire after helping the latter find his way home.

Melissa Benoist plays Supergirl in the CBS series and she reveals her thoughts about her character meeting Grant Gustin's Barry Allen/The Flash. In a statement in a featurette (via TV Line), Benoist said that the duo had such good chemistry, as there was joy, humor, and lightheartedness about them.

Also, the promo clip for "Supergirl" season 1 episode 18 is set to see Kara's friends react in various ways. Winn (Jeremy Jordan) is more than thrilled upon knowing that Allen comes from another realm while James is left curious on how the scarlet speedster travel that fast. According to the publication, the preview also featured a "Three Musketeers" references from The Flash, along with a "scary turn" from Siobhan's Silver Banshee.

In other news, fans might also see Wonder Woman in National City. In their interview with Entertainment Weekly, series executive producers Andrew Kreisberg and Greg Berlanti said that they had had the perfect role for Lynda Carter, adding that they could not work out her schedule. "Next year," Berlanti said.

Kreisberg also said that they were going to do it and they would just do it next year. Berlanti also added that Carter could be the female president of the United States in the series.

"Supergirl" season 1 episode 18, "Worlds Finest" is set to air on Mar. 28 on CBS.