Cat Grant with Clark Kent
I am now 100% positive that when Cat flirts with Clark, especially in the season 2 finale, she is just making Kara jealous.
Cat knows Kara is Supergirl, so she probably knows Clark is Superman. It’s not that hard to figure out. So Cat is talking to them in a way that doesn’t let them know she know’s Kara’s identity, specifically, but also gets the message across that she believes in Supergirl.
So since in that whole scene, she is talking with a subtextual message, I believe the line “Oh those big green eyes; I promise you when he takes off those glasses he is a tiger in bed” is actually how she feels/thinks about Kara. But she changes a few words to fit Clark so she doesn’t scare Kara away.
However, while she says that line she is looking at Kara in a way that says ‘I’m talking about you’. But Kara is too blinded by her jealousy to realise it. When Kara then awkwardly chuckles and says “Oh god, I hope Rhea kills me”, it clearly shows she is jealous by the events of the scene.