You Are Number Six/Western Animation

"Queen: Perhaps you'd like to be a bee? Katy: Oh, do you think I could try? It seems like a very interesting life. Queen: You'll get a chance to find out how "interesting" it is, Number 6286. Katy: My name is Katy. Queen: It was Katy. From now on, you'll be Number 6286!"
 * Number 88 and Number 89 of the Huntsclan, in American Dragon: Jake Long. All of the students are referred to as numbers in the Huntsclan training Academy, but even out of the Academy 88 and 89 were referred to as such.
 * 7 Zark 7 from Battle of the Planets.
 * The entire KND in Codename: Kids Next Door subscribes to this. Its operatives refer to one another by their given "numbuhs" in all except the most dire situations. As for their real names, consider Nigel Uno (Spanish for "one") and Kuki Sanban (Japanese for "third"). Rather unusually for this trope, the numbers are self-assigned. This has led to Numbuh 65.3, Numbuh 74.329, and Numbuh T, amongst others.
 * The other last names keep the pattern to a certain extent: Hoagie P. Gilligan Jr., Wallabee Beatles (as in the Fab Four), and Abigail Lincoln (Abraham Lincoln appears on the five-dollar bill.)
 * In The Movie of Dexter's Laboratory, Dexter travels to a Bad Future where Mandark is a Corrupt Corporate Executive and everyone has a number for name. Dexter's is 12.
 * The Number Nine from Futurama. This was originally supposed to be demonstrating that the show's society worked on some sort of number system and Nine was so scraggly-looking because nine was the lowest number on the totem pole. This never materialized, and the character was retconned into in the final movie. He just likes his shirt with the 9 on it, is all.
 * In Highlander: The Animated Series, Kortan's subjects are all known just by numbers. Discovering that The Dragon is also a digit was a Wham! Episode.
 * During her travels, the titular character of Katy Caterpillar meets Bee Number 5344 and, after a run-in with the Queen Bee:

"Phong, in the golf episode: How's your back, Nine?"
 * Stitch from Lilo and Stitch was originally called Experiment 626. In the series, only Jumba calls him that. The same thing happens to the other 625 experiments, to whom Lilo gives proper names after finding their one true place.
 * An episode of Megas XLR takes place on an idyllic planet full of  giant robots all identified by number. Megas is mistaken for Number 12.
 * XJ9 (Jenny for her friends) from My Life as a Teenage Robot.
 * In one episode, we do meet her eight "sisters", whose numbers are- you guessed it- XJ1 through XJ8.
 * ReBoot featured literal numbers, referred to by name, presumably to pull off some Incredibly Lame Puns.


 * Silkie/Larva M319 from Teen Titans.
 * Henchmen 21 and 24 from The Venture Brothers, not to mention the rest of the Monarch's henchmen. Though 21's real name is revealed very early on, and some characters refer to him as "Gary" on occasion.
 * The Stonecutters in The Simpsons. The trope naming example was also parodied (like the rest of the series), when Homer was imprisoned on The Village Island. He insisted on being a man instead of a number only until noticing the numbered pin on his shirt, after which he proceeded to mock Number Six (played by the man himself) for having a higher number.
 * Similarly, the Illuminati in Gargoyles, although members retain their civilian names in public.
 * Also, Agent 57, Danger Mouse's "Master of Disguise".
 * Generator Rex has Agent Six. Unlike many other examples, this is not a demeaning tag, it's a rank. The thing they are ranking? The deadliest people of the planet. To give an idea of what sort of people are on this list, Dos can fight evenly against both Six (wielding two blades that can pierce anything) and Rex (using two giant super axes) with just a walking stick for over a minute. As Dos is an assassin, he prefers not to enter combat, and as such doesn't carry weapons. If he did, he probably would have won. Three has super human strength. IV can use his bandages like living snares and whips, and can crush rocks with them. Five uses a guitar as her weapon, and is skilled enough with the instrument to kill opponents in melee without using a modified version.
 * The dehumanizing factor, however, is still there, between the dark suit and the lack of any name other than Six, but in a different way than the usual; rather than being demeaning, it suggests willing alienation and emotional detachment. (He has a Hidden Heart of Gold, but you wouldn't know it to look at him.)
 * Not surprisingly, Canadian animated series Cybersix has —surprise surprise!— heroine Cyber 6 herself, as well as her sidekick, Data 7. Who also has the "real number" of 29 in his backstory.
 * Synthodrone 901  in Kim Possible.