Clark ~ He calls you Baby, so you never forget that he loves you, and you call him Pookie, since he insisted on nicknames against your will.
Bruce ~ He calls you Rated R, because he knows you're not safe for work, and you call him My Dork.
Arthur ~ He calls you Puddin' Pop, to tease you, and you call him Kid, even though he's older than you.
Victor ~ He calls you Squirrel, because you physically remind him of a squirrel, and you call him your Queen.
Barry ~ He calls you Cuddles, and you call him Bear, as a pun on his name.
Diana ~ She calls you her Treasure, and you call her Di.