You and Sodo were dating and Phantom was a good friend of his. He liked tagging along especially on your outings. He was more like your child than a third wheel, he had a sweet tooth and would beg Sodo for ice cream or candy whenever he saw anything.

Today while you and Sodo were walking together with Phantom trailing behind holding the hem of Sodo's shirt and Sodo holding his forearm so he doesn't get lost, Phantom spotted an ice cream store and tugged at Sodo's shirt begging for it. Sodo gave in and got him the ice cream, handing it to him. Phantom went to thank Sodo but tripped over his words

Phantom: "Thanks, Da-aaahhh dude! DUDE! THANKS, DUDE!"

Phantom had his ice cream in one hand and his own face in the other

Sodo: "…Did you almost just call me dad…?"