Pluralses

Sometimes a characters will display their lacks of eloquences (or lack of familiarity with the English languages) by randomly pluralising words that frankly don't needs pluralising (including wordses that are alreadys pluralses). This tends to go with improper verb conjugation too, sometimes completely nonsensically. eg, instead of "I am a troper", expect to see "I are a tropers" or "I ams a tropers".

A Subs Tropes of You No Take Candles. Compares Confusings Multiples Negativeses. Not to be confused with loanwordses that have several possible pluralses such that one does not know which one is right (Latin-ish words, etc.).

Exampleses:

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Famous meerkat-comparing meerkat Aleksandr Orlov's catch phrase is "Simples."

Animes and Mangas

Momoko from Saki is subtitled as adding random plurals to her words. Though in this case it's not so much a habit of unnecessary pluralysis as it a Verbal Tic where she ends words with "-su."
Tsuruya tends to do this in fanworks, though her Verbal Tic is a bit more complex.

Comics Bookses

The Gronkses in Strontium Dog all do this.

Fans Workses

The Spiderses.
This is one of the distinguishing features of house-elf dialogue in the Harry Potter fan fiction of Doghead Thirteen.

Filmses

The infamous "Backstroke of the West" bootleg of Star Wars: Revenge of the Sith gives us the subtitle "Send these troopseses only." It also gives us such words as "dreamses," "needses," "beened," "livinging," and the especially wonderful "politicseses."
In Love Actually there's a scene where Colin Firth has learned clumsy Portuguese so he can tell his housekeeper he's in love with her and ask her to marry him. She says, "Thank you, that will be nice," and then when he remarks that she learned English too, she says, "Just in cases."

Literatures

The Lord of the Rings Gollum and Smeagols does this all the times, yes, filthy hobbitses, yes they doessssss...
- Played with in the Riff Trax version of The Return of the King, wherein "the plural of 'hobbitses' is 'hobbitseses '"
In Me Talk Pretty One Day, David Sedaris chronicles his experiences learning French as an adult, which includes some of this.

Things began to come together, and I went from speaking like an evil baby to speaking like a hillbilly. "Is thems the thoughts of cows?" I'd ask the butcher, pointing to the calves' brains displayed in the front window. "I want me some lamb chop with handles on 'em."

Discussed and Defied in the Dresden Files novel "Death Masks". When Harry needs to refer to more than one Elvis, he explains that he will be using the faux Latin plural "Elvii" because using the correct English plural "Elvises" would make him sound like Gollum.

Lives-Actions TVs

One time on Sha Na Na, Chico was being given the Pygmalion treatment so he could ask out a higher class broad; for him the equivalent of "The Rain in Spain Stays Mainly in the Plain" was to say, "Here you go," instead of "Here youse go" when passing the potatoes.
The "Shoe Shop" sketch in A Bit of Fry and Laurie has: "I dislike the word 'brothel', Mr. Jowett. I prefer the word 'brothels'. Yes, this is a brothels."
- In the "Flowers for Wendy" horror-parody sketch, the narrator goes into this toward the end for no real reason: "A tale of walking home, and pavements, and forgettings of birthdays, and rememberings, and wantings to buy flowerings, and discoverings of a flower-stallings just at the right momentings."
In one of J.D.'s daydream sequences on Scrubs, he was a Mexican migrant worker talking about "apples pie" and "apples juice."
A Running Gag for Wheel of Fortune host Pat Sajak whenever a plural category comes up is to do something like "Our category is Living Thingseses."

Videos Gameses

The Hypello in Final Fantasy X do this. You rides the shoopuff?
In the subtitles, all the Gamorreans [pig people] in Knights of the Old Republic use this trope in their speech.
The Big Bad in the first Thief game, "The Trickster", talked this way. Something of an aversion, as he spoke refined English in another guise. The Pagans from Deafly Shadows (who worship the Trickster, among other things) are a straight example.
Jedi Outcast has the Chiss bartender on Nar Shadda talk like this, leading Kyle to comment on how you should "Never trust a bartender with bad grammar."
- Trulies.
Some fanworks have Marisa Kirisame's "-ze" Verbal Tic as a sort of "-s" sound at the end, so "Reimu, ze" becomes "Reimus", and so on.
Faxanadu's "You do not have enough golds"

Webs Comicses

The titular character from Selkie has this, though given her physiology, it's not surprising.

Westerns Animations

Sal in Futurama does this to emphasise his lower-classness.
In Metalocalypse, Skwisgaar Skwigelf and Toki Wartooth do this alls the times to reminds yous that they're from Europes.
According to Pinkie Pie, the plural of "pegasus" is "pegaseseseses".
In older episodes of The Simpsons, Homer usually addresses the Flanders family as the Flandereses

Reals Lifes

Two words: The Internets.
- Teh Internetz, shurely?
  - Oh noes!
This can be common when words are borrowed from other languages. For example, a single Börek (a type of pastry from the Balkans) is known in Israel as a "Bourekas", which is in fact the plural form of the original word. So the plural form of Bourekas in Hebrew is "Bourekasim" (with "im" being one of the two common plural suffixes in Hebrew).
- This often happens when Italian foods are served in English-speaking countries. In Italian, ending words with the letter "I" indicates plurality, but in other countries, it's quite common to ask for a biscotti, panini, cannoli, etc.