This was one line that really stuck out in The Return Of Harmony for me. I loved the flirt in Discord's voice when he said "Did you miss me, Celestia? I missed you." from the stained glass windows. I'm a big Dislestia shipper, and I have a feeling that Discord likes Celestia, maybe even before he was reformed. Maybe even thousands of years ago when he enslaved Equestria. The way he said it to her just sounded so flirtatious.