It was Christmas and Mettaton wanted to have a little fun with the skeleton boy He had been crushing on for the past 3 years. So mettaton put on a christmas outfit slightly skimpy and switched the tune and began to hum along 

"Sansta baby, Slip your joy buzzer under the tree, for me. Be a good robot all year Sansta baby so hurry down the chimney tonight" He snickered noticing sans face turning blue. 

"Sansta baby, A spotlight too make that pink too~ Ill wait up for you dear Sansta baby. So hurry down the chimney tonight" He sat down on the edge of Sans chair. and began to walk his fingers along the back 

"think of all the shows iv missed, think of all the monsters that I haven't kissed. Next year I promise to be just as good if you promise to check off my christmas list" He turned Sans face towards his and began to purr. 

"Sansta baby, I want a speaker so you can hear me dear, iv been a angel all year Sansta baby so hurry down the chimney tonight" Mettaton got into Sans lap with a seductive growl. 

"Sansta honey, Oh just one little thing I need, A steed. to steal you away for the night Sansta baby, So hurry down the chimney tonight" She ran her finger along his jaw and his face was blue

"Sansta cutie, and fill my stocking with laborginies too... for you. Sign on the dotted line Sansta baby, so hurry down the chimney tonight" She brought sans face close to his

"Come trim the stages tree with my decorations from Gucci... I really do believe in you darling~ Lets see if you believe in me" His voice was no more than a growl as sans was lulled into a state of seduction. 

"Sansta baby, I forgot the last little thing... A ring.... not on the phone... Sansta darling... so hurry down the chimney tonight" He kissed sans on the corner of the list. He was just seduced and like frozen with a blush on his face. "see you in my room for christmas darling. and we can unwrap some extra gifts" Mettaton purred getting off his lap. 

After about 5 minutes of Sans sitting there confused and paralyzed he muttered "i have the weirdest BONE-r right now" He flops onto the couch unsure what just happened