Ear Worm/Theatre/Gilbert and Sullivan

Gilbert and Sullivan wrote fourteen operas together, and there's at least one Ear Worm in every one of them. For instance:

Thespis

 * "Olympus is now in a terrible muddle/The deputy deities all are at fault..." sticks in one's head even with the music lost.

Trial by Jury

 * "For I am a judge/And a good judge too..."

The Sorcerer

 * "Ring forth, ye bells/With clarion sound/Forget your knells/For joys abound..."
 * "My name is John Wellington Wells/I'm a dealer of magic and spells..."
 * "Thou hast the power thy vaunted love/To sanctify all vows above..."
 * "Oh, I have wrought/Much evil with my spells/And ill I-I can't undo..."
 * "Oh, joyous boon! oh, mad delight!/Oh, sun and moon! oh, day and night!"
 * "Alas, that lovers thus should meet/Oh, pity, pity me!"

H.M.S. Pinafore

 * "I am the monarch of the sea/Ruler of the Queen's Na-vee/Whose praise all of Great Britain chants"/"And we are his sisters and his cousins and his aunts!"
 * "When I was a lad I served a term/As office boy to an attorney's firm..."
 * "A British tar is a soaring soul..."
 * "Never mind the why and wherefore/Love can level ranks, and therefore/Though his lordship's station's mighty/Though stuPENDOUS be his brain..."
 * "For he is an Englishman!"

The Pirates of Penzance

 * "Oh, better far to live and die/ Under the brave black flag I fly/ Than play a sanctimonious part/ With a pirate head and a pirate heart..."
 * "How beautifully blue the sky, the glass is rising very high..."
 * "Iiiiiiiiiiiiiii- am the very model of a modern major general..."
 * "When the foeman bares his steel"
 * "Tarantara, tarantara!"
 * "We uncomfortable feel"
 * "When you had left our pirate fold/ We tried to raise our spirits faint/ According to our custom old/ With quips and quibbles quaint..."
 * "When a felon's not engaged in his employment (his employment) or maturing his felonious little plans (little plans)"
 * "WITH CATLIKE TREAD! UPON OUR PREY WE STEAL!"

Patience

 * "If you want a receipt [sic] for that popular mystery/Known to the world as the Heavy Dragoon..."
 * "In a doleful train/Two and two we walk all day..."
 * "If you're anxious for to shine/In the high aesthetic line/As a man of culture rare..."
 * "Come walk up and purchase with avidity/Overcome your diffidence and natural timidity..."
 * "It's clear that mediaeval art/Alone retains its zest..."
 * "If Saphir I choose to marry/I shall be fixed up for life..."
 * "So go to him and say to him with compliment ironical..."

Iolanthe

 * "Go away madam/I should say madam/You display madam/Shocking taste..."
 * Really, the entire Act I Finale.
 * "When you're lying awake/With a dismal headache/And repose is tabooed by anxiety..."
 * Be sure to check out the Todd Rundgren version.
 * "Soon as we may/Off and away/We'll commence our journey airy/Happy are we/As you can see/!"

Princess Ida

 * "Search throughout the panorama / For a sign of royal Gama / Who today shall cross the water / With his fascinating daughter / Ida is her name!"
 * "If you give me your attention I will tell you what I am/I'm a genuine philanthropist all other kinds are sham."
 * "Gently gently evidently we are safe so far/After scaling fence and paling here at last we are"
 * "This helmet, I suppose / Was meant to ward off blows..."

The Mikado

 * "If you want to know who we aaaaaaaaaaaaaaaare, / We are gentlemen of Japaaaaaaaaaan..."
 * "As someday it may happen that a victim must be found/I've got a little list/I've got a little list..."
 * "To sit in solemn silence in a dull dark dock / In a pestilential prison with a life long lock / Awaiting the sensation of a short sharp shock / From a cheap and chippy chopper on a big black block!" So earwormy, Pink Floyd just had to sample it.
 * "A more humane Mikado never did in Japan exist/To nobody second/I'm certainly reckoned/A true philanthropist."
 * "Three little maids from school are we, Pert as a school-girl well can be, Filled to the brim with girlish glee, Three little maids from school..."

Ruddigore

 * "If somebody there chanced to be/Who loved me in a manner true..."
 * "Welcome, gentry/For your entry/Sets our tender hearts a-beating..."
 * "You understand/I think I do/With vigor unshaken/This step shall be taken..."
 * "When I'm a bad Bart. I will tell taradiddles/He'll tell taradiddles when he's a bad Bart..."
 * "When the night wind howls/In the chimney cowls/And the bat in the moonlight flies..."
 * "Henceforth all the crimes/That I find in the Times/I've promised to perpetrate daily..."
 * "My eyes are fully open to my awful situation/I must go at once to Roderic and make him an oration..."
 * "I shipped, d'ye see, on a Revenue sloop..."

The Yeoman of the Guard

 * "When jealous torments rack my soul/My agonies I can't control/Oh, better sit on red hot coal/Than love a heartless jade."
 * "Oh a private buffoon is a lighthearted loon/If you listen to popular rumor..."
 * "Tower warders, under orders, gallant pikemen, valiant sworders!"
 * "I have a song to sing, O!" "Sing me a song, O!"
 * "Heighdy, heighdy, miserey me, lackadaydee!"

The Gondoliers

 * "There lived a king as I've been told/In the wonder-working days of old/When hearts were twice as good as gold/And twenty times as mellow..."
 * ”Oncely, twicely, oncely twicely!/ That is the style of thing precisely.”
 * "Then one of us will be a queen and sit on a golden throne..."

Utopia, Limited

 * "In every mental lore/'Tal lore/The statement smacks of vanity..."
 * "Society has quite forsaken all her wicked courses, / Which empties our police courts and abolishes divorces. / (Divorce is nearly obsolete in England!)"

The Grand Duke

 * "By the mystic regulation/Of our dark Association/Ere you open conversation/With another kindred soul/You must eat a sausage-roll!"
 * "When you find you're a broken-down critter/Who is all of a trimmle and twitter/With your palette exceedingly bitter/As if you've just bitten a pill..."
 * "Big bombs/Small bombs/Great guns and little ones/Put him in a pillory/Rack him with artillery..."
 * "Take my advice - when deep in debt/Set up a bank, and play Roulette!"