A local newspaper’s web site has a daily poll you can participate in that is often interesting. It generates a bar graph, just like here. Of course, after you make your choice, you have to answer another question or two about consumer goods, politics, etc.
Today’s poll was the title. The choices were:
__ Yes
__ No
__ I can’t recall
They should have gone with:
__ Yes
__ No
__ I can’t recall
__ Zri scanispel ito. Glick!
Dennis
Yes, I did create the bare bones of a language when I was about 13, just for fun.
But what you are citing is more “making up nonsense words in real time.” There’s a word for this – I can’t remember the word right now* – that’s at least used when it’s a neurological condition.
When I was 17, I had two friends who were good at this (especially when stoned) – it sounded like they were having a normal conversation (intonations, etc.), without a single real English word. I still remember one word they used (made it into the high school yearbook, even): rehebusnirt.
*though I’m tempted to make one up!
It’s “neologistic paraphasia.”
No, I didn’t just make that up! 
Here’s a generator of such gibberish, based on a story by Borges, but it doesn’t have the sound patterns of English, the way you or I would make up words.
No, but I made a symbol that represented me 40 years before Prince.
And what is really weird about that, is the one he made has striking similarities to mine. See for yourself. Go find my Junior High text books. It’s all over them.
My wife and I have what we call “code sounds” like “geg” for “lets get out of here” and about a dozen like that but nothing like a complete language.
Now back in my college days I helped a Professor develop a course to teach teachers how we learn math. It used Greek symbols for the written numbers and operated in base five. A few folks, after stumbling and frustrating themselves through basic addition and all really clicked to the whole thing and by the end of the semester were doing calc and trig in it. I don’t know if he ever published anything but the class title became “Mathematics as a foreign language”.
Sure did. Doesn’t every true nerd do that in high school?
You’re at the age where you know just enough to get something passable, but not enough to make it realistic.
Mine had an attempt to use consistent, non-English grammar and sentence structure. I still have a couple bits of the written version somewhere, but I’m sure I can no longer read it!
Not so much making up a language from scratch … but I do twist and torque the Englishing language until she screams in agony and defeat … does that countate?
No, but I do make up my own entertainment - like betting myself that, within 3 posts, someone would reply in gibberish.
Alas, again I lost. I have to do all my chores for me for a week now. 
My daughter did. I don’t think it was anything like a complete language. One word I recall was “gulamorg” for “good morning”. She styled herself “The founder of Uffala” and the language was Uffalese.
Not a made-up language of our own, but in Grade 7 one girl taught us all a language that her mom taught her - it was called “giddy-gee” (hard g sounds.) You pretty much inserted “dda” in between syllables of a word - for instance my user name would be pronounced “s-odda-goy-lidda-gee-edda-gent.” A bunch of us girls were fluent and to this day I can still speak it.
Discussions of this sort always call for a link to Prisencolinensinainciusol by Adriano Celentano (1972).
When it’s intentional, it’s Glossolalia, aka the grand religious tradition of “speaking in tongues.”
Love it! Funk-ayyy pseudo-English by Italians.
And many nerds continue on to creating Conlangs as a hobby. When the topic has come up before, I recall there are a few Dopers into it. (There seems to be an overlap with Tolkien aficionados.)
Growing up, until the age of four, I had a language that only my brother and I understood. Would not speak English, I would look at my brother and say something like “una gotte bitey doh”, whereupon people would look at Jim and he would say “he wants more milk”.
Did this until the day I learned to read - my first sentence in English was in Daytona Beach when, driving down the road with the fam, I blurted out “H O T E L… what do dat spell?” People fucking lost it and my Dad almost got into an accident. Good times.
I pretty much never spoke the language after that and have largely forgotten it except for some basic phrases.
No complete languages but I’ve done some words for the Finish the Sci-Fi Story threads and the Finish the Sword & Sorcery Story thread.
I write (or attempt to write) sf and fantasy stories, and so I’ve made up a lot of “alien” and “magical” words. It’s quite a lot of fun!
Made up an alphabet, with symbols for some digraphs like th and ch.
Brian
Not saying we made it up, but in junior high school my friends and I would put an “ib” in front of every “audio” vowel in the words we used in conversation.
“Do you understand me?” became “Dibo yibou ibundiberstiband mibe?” Even individual words were incomprehensible to “outsiders”. “When” became “whiben”, where - whibere, who-whibo, etc.
We became quite fluent in it much to the chagrin of our parents and teachers.