Making an ERB. Give me all the lore you got on these two champion couples, please!

I'm creating League epic rap battles (thought it'd be fun). The first one I'm thinking of attempting is Xayah and Rakan versus Katarina and Garen (if you have a better couple IYO, suggest away however!). I can read up on their lores and I know a good amount of references, but not everything and hardly the deeper digging stuff. Would anyone care to help tell me or direct me to all the lores the aforementioned champions are in, or all/any inside jokes with them?

VS