"He's cute!" Jane excitedly says in the clip, while pointing at a picture of Harington on a computer.
"Did you know you have a rabid toddler fan base?" Kimmel joked with the star.
"No, this is new to me," Harington quipped. "This is great!"
In celebration of the show's return, Kimmel also gave fans a look at some of Harington's original taped auditions, when he tried out for some different, surprising roles -- including Cersei Lannister (in a blond wig), Tyrion Lannister (by walking around on his knees), and Daenerys Targaryen (in a different, blonder wig).
Obviously these audition tapes are just a joke, but Harington's quip about Harry Potter joining the Game of Thrones universe would make many fans lose their minds.
Check out the video below for a look at the funny snapshot.