This is based off of a picture on Deviantart. The credit for this idea goes to Breetroad. The picture is called "Bunny and Jack Happy New Year". This is my guess as to what was said.
Bunny was having a very lovely dream about carrots when he felt a cold chill. Jack was near, he could tell. It never got cold in his Warren unless Jack was there. Bunny cracked his eyes open, turning on his side. Jack was standing at the enterance to his bedroom, pillow hugged tightly to his chest. The winter spirits hood waas pulled over his head, telling Bunny that he was cold.
"Hi… Bunny." Jack's face flushed a little.
"What's wrong, Jack?" Bunny asked groggily.
"I…I can't sleep…" He licks his lips and continues. "A-and it's too cold to sleep outside…"
Bunny pauses, then nods.
"Um, could-could I—?" Jack blushes furiously, losing all his will to speak.
The Hope bringer smiled softly, patting the spot next to him. "You can sleep here anytime. Anytime, frostbite."
XxXxX (This wasn't part of the picture)
Sandy grinned as he sprinkled dreamsand over Jack and Bunny'a heads.
The two were snuggling, Jack's head buried into Bunny's soft, furry chest. Bunny held his arms around the boy protectively.
Their dreams mixed and Jack and Bunny were having a snowball fight while munching carrots. Sandy laughed silently, a heart appearing above his head.
Sweet dreams…