Walter Plinge is a knock-kneed buffoon and general dogsbody at the Ankh-Morpork Opera House who appears in Maskerade. He wears a beret and has absorbed opera until it subsumes his soul. He is the butt of jokes by his fellow theatre stagehands and has a doting mother who keeps a close watch on him. His character is based on the figure of phantom of the opera in the musical by Andrew Lloyd Webber of the same name. In Maskerade, he is in fact the second Opera ghost, not the evil one who kills for money, but the one who sings like an angel and composes a whole series of a new style of musical entertainment. Like the other people in the Opera house Walter has a certain degree of Opera-connected madness, but unlike everyone else when he puts on his mask his awkwardness and social ineptitude vanish and he becomes 'the opera'. The connection is so strong and deep that when Granny Weatherwax reaches out to the Opera with her mind and brushed Walter's own mind, she described the connection as two entities being fused together. Because of this both of Walter's personalities have a deep love of the Opera house and everything related to opera. So much so that the Ghost's lair beneath the stage is filled with old and discarded props and costumes that he spends time repairing. The location of the lair allows the music to filter down and "fill the soul". Walter's connection with Opera also causes him real pain when the Opera is stopped before it finishes - Walter physically and mentally hurt by it knowing that the show must go on.
After the death of Mr. Salzella, Walter is no longer the errand-running figure of fun whose mother worries about him but the new Director of Music at the Opera, although he continues to clean the toilets and sweep the theatre as before.
In London theatres, the name Walter Plinge is used as a pseudonym when a part has not been cast, an actor is playing two parts, or an actor does not want his or her name in the programme. It has been suggested that Plinge was a real London publican, honoured by a group of actors with the borrowing of his name but there is no evidence to support this theory. The name has also been used occasionally in American theatre, as has the more popular George Spelvin. Similar pseudonyms are David Agnew at the BBC and Alan Smithee in Hollywood. A Sir Walter Plinge is also the resident ghost of Imperial College Union's Concert Hall, and is regularly thanked in programmes by the ICU Dramatic Society (DramSoc) for watching over them. The use of the name is clear foreshadowing that Walter has two roles in the novel, the bumbling janitor and the opera ghost.
The character and appearance of Walter Plinge owes a lot to the character of Frank Spencer, in the long-running BBC sitcom Some Mothers do Have 'Em. (The mother in question might have been a despairing Mrs Plinge.) Spencer is a gormless child-man, who bungles into unusual humorous situations and somehow manages to extricate himself unscathed in spite of the general destruction all around him. Like Walter, he affects a shapeless trenchcoat and beret. He was played by Michael Crawford, who coincidentally went on to international stardom in The Phantom of the Opera. Crawford going from shambling cloddishness to physical grace and presence in one very smooth transition, almost as if donning a mask effected the transformation.
The stagehands hiding Walter's broom is evocative of the film The Last Picture Show, which follows a group of young American school friends through graduation from high school into adulthood in a tiny Mid-Western town. One of the group, who will never see adulthood and is fated to be an eternal child, is what used to be known as a "retard", a simple boy who will actually go out with a broom and seek to sweep the street. Generally speaking, his peer group are protective of him, but he is the butt of unthinking cruelty on occasion. Walter's desire to keep on cleaning the toilets even after his promotion to music director is also reminiscent of Stanley Spadowski, another ungainly man-child janitor whose unlikely talent is discovered under silly circumstances in the 1989 film UHF.