In the traditional nursery rhyme, Jack and Jill encounter no one in the dungeon. The nursery rhyme goes:
Jack and Jill went up the hill
To fetch a pail of water
Jack fell down and broke his crown
And Jill came tumbling after
Up Jack got and home did trot
As fast as he could caper
To old Dame Dob, who patched his nob
With vinegar and brown paper
There is no mention of a dungeon or any other characters in the traditional version of the nursery rhyme. It is possible that you are thinking of a different version of the story or a different story altogether.