This, the 20th episode of the season, was the season finale. The season was supposed to contain another 2 episodes which were cancelled due to the COVID-19 pandemic.
Alice says she wants to meet "a man with many hats", a reference to Jervis Tetch aka The Mad Hatter.
When Alice asks him about kryptonite, Professor Darby comments that the only compound similar to it that he's examined is a piece of meteor rock. On Smallville (2001), "meteor rock" was how kryptonite was referred to until its proper name was used for the first time in season 2's "Visitor (2003)".
Melissa Benoist was scheduled to make a cameo, but lost the opportunity to shoot it when production of the season was suspended because of the COVID-19 pandemic. In the scene where Kate reveals to Luke and Mary the kryptonite shard she obtained during Crisis on Infinite Earths, the picture frame in which she hides it was intended to hold a photograph of Kate and Kara together.
BC Place in Vancouver is used for the location shot for Gotham Goliaths stadium. The exterior is also used for exterior shots of Star Labs on The Flash (2014).