In Supergirl S1E3, Kara mentioned watching Homeland. Her actress Melissa Benoist guest starred in that series, with her first appearance in S1E2, followed by her second and last appearance in also S1E3
Melissa Benoist | The Werewolf Diaries Wiki | Fandom
Supergirl Season 4 Episode 16 – Melissa Benoist as Kara/Supergirl | Tell-Tale TV