Unlike Mr. B, Miss M has nice lanky legs that enables her to go up and down the stairs with ease. Her issue with the stairs is the troll that lives on the stairs leading to the basement. It is purely coincidental that the troll appears whenever A or I are on the stairs to the basement.
According to Miss M, this troll strokes the luscious fur on her rear whenever she is laying in the bed by the stairs. A and I have yet to see this troll that she speaks of. Though we know when the troll strikes, because Miss M will quickly jump out of the bed, shake and lick her lips.
Unlike Miss M, whenever the troll strokes Mr. B, he just smiles and enjoys the pets from the troll. The only troll he fears is the one named Miss M.