Every now and again, some unsuspecting editor will add an example to a trope page without checking to see if that page contains an example from that series already. If it does (especially if the example itself is repeated), that page becomes an example of this trope, albeit usually only temporarily.
Not just in posts, either: 1: go to the top of this page. 2: Click "go to watchlist" (need to be a known troper) 3: Look at the top. You should see a button that says "recently new."
And then when people find out, instead of removing it, they tend to Natter on about it. Or they explain everything that was already stated a second time because they think the first guy got something wrong.
I just move the two examples next to each other. Especially when the later one asks why this example hasn't been mentioned yet.
The inverse also happens. On a page for a show, a trope with multiple names may be listed twice. For example, ever since they started calling it Hilarious in Hindsight, it's often seen on a page that also has Reverse Funny Aneurysm. Even worse when someone notices the Reverse Funny Aneurysm example and renames it without realizing there's already a Hilarious in Hindsight example.
For some reason, several pages on this very wiki have links to themselves. Occasionally the very first words on a work's page.
There's also an annoying tendency to have a phrase like "Of course, Your Mileage May Vary" added to the end of examples on pages devoted to YMMV examples.
Since TV Tropes introduced namespaces, some page names are this. Films with "film"/"movie" in the title, comic books and strips containing "comic", wikis, blogs...
Nowadays, most pages are sorted by media. But in some cases, you have an example in e.g. the film folder, obviously linking to a page in the film namespace, which still mentions that work X is indeed a film. Justified when it's The Artifact from a time when the page wasn't sorted and the page not yet namespaced.
There's a redirect to this page titled Redundancy Department of Redundancy.
Warning Labels That Provide Warnings on their Labels
Any time there's a peanut butter jar or a labelled peanut container that says "Warning: May contain peanuts."
Amusingly, peanuts aren't actually nuts, which puts an interesting spin on the traditional 'may contain nuts' warning. In particular "This product was made in a place that processes nuts and peanuts".
If it said 'contains peanuts', that would be one thing. The real headscratcher is that it seems to suggest that it might not.
The British product Sun-Pat Peanut Butter, in a real headscratcher, now says 'peanut spread' on the packaging, and in the description, says 'contains absolutely no butter'. You wonder if they are marketing themselves to aliens.
Because of regulations or lawsuit-related ass covering, in the US a lot of food products that obviously have a product in them (Peanut M&Ms have peanuts!) have this trope in action on their packaging. Like milk or cheese labeled "Contains Dairy product."
Although it is somewhat valuable to people with serious food allergies, in that some products don't actually contain what you think they obviously should. For example 'honey nut' Cheerios don't contain nuts and in various times in their production history did not contain honey.
Warning on sleeping pills: "This product may cause drowsiness. If affected, do not drive or operate machinery."
A variety of products, including baby shampoos and Mr. Bubble— a brand especially made and promoted for children— are labeled "Keep out of children's reach".