Mrs. Gammliss

Mrs. Gammliss is a neighbor of Mario and Luigi's, who lives in apartment 5C of the building that Mario Brothers Plumbing is located in. Somewhat deranged, Mrs. Gammliss believes that she's an opera singer, when in actuality, her singing is quite poor, to the point where much of it is incomprehensible and capable of shattering glass. Due to her obsession, Mrs. Gammliss almost always sings in place of normal talking.

History
Little is revealed about Mrs. Gammliss' backstory, except that she became notorious towards her neighbors due to her poor attempts at singing. During the events of "Opera", Mrs. Gammliss' voice found its way down the building's garbage chute and into Mario Brothers Plumbing one morning, waking up Mario and Luigi in the process. Unaware that her singing was bringing much grief to the Mario Bros., Mrs. Gammliss continued and showed no sign of stopping.

Unable to escape from Mrs. Gammliss' voice, Mario, Luigi and even the Ratigator attempted to shield themselves by wearing earmuffs, but were unsuccessful in doing so. Mario eventually called up to Mrs. Gammliss through the garbage chute, explaining that her singing was driving them crazy. Mrs. Gammliss appologized, but her voice managed to break a glass that Luigi had been holding in the process.

After Mrs. Gammliss refused to cooperate after being asked to lower her voice for a second time, Mario decided to fight fire with fire, and accompanied by Luigi, the two of them sang several high notes back up the garbage chute at Mrs. Gammliss. Their singing resulted in a crashing sound from Mrs. Gammliss' apartment, and she begged them to stop, as their voices were destroying her apartment. Mario agreed that he and Luigi would stop if Mrs. Gammliss would stop as well, and the two parties managed to reach an agreement.

Trivia

 * Mrs. Gammliss is the only guest star on The Super Mario Bros. Super Show! to not make an onscreen appearance.