Ok this is not designed to be a serious game or even a game at all, just a light hearted idea/piece of fun perhaps.
It could be played within an evening and you and your group would probably only play it once. But it goes something like this (very short I know)... (this post is written from the perspective that you are going to run the game).

Players get to make their characters, any characters will do, using any system, you could even spring this on players after they have made their characters for a new storyline, or anytime when some players have made new characters (perhaps your swapping system? who knows?).

-Now when your players are ready to start, "wait sorry guys, change of plan, change to the system!"

Tell the players to take their characters (and they are not allowed to speak to each-other or collaborate on this, make them go to different rooms if necessary).

-Tell them each player can come up with 7 things his character is allowed to say, these can be single words or phrases up to 10 words long, hyphenated words, parts of words, however players care to cheat when making these 10 word or less phrases it doesn't really matter.

-When speaking in game the characters can string together these words/phrases however they want, however they must complete each phrase every-time they say it. They cannot stop half-way or start half-way through one of their phrases.

-If a character wants to make any action other than walking in the game he must be able to say it, For instance if a player wants his character to stab something with his sword his character must be able to say "I stab it with my sword".

-In the game the characters are not allowed to say anything other than these 7 phrases, & of course meta-gaming should be discouraged aswel.

Now what you have planned for them are simple quests/scenarios that will required some talking.

The players win if they successfully complete the quest at hand no matter how they choose to do it.

As the GM/DM you can role-play all the npc's with no restrictions. And as a npc you should be very awkward/frustrating for the players (in a humorous way) but also reward them when they come up with a good idea.

The quests/scenarios should be very simple with very clear objectives,

Anything from

npc "hey I have a riddle I'll give you a gold piece if you solve it, do you want to hear it" 
Player "I stab it with my sword"
npc "eck what? why are you going to stab me"
another player "I think its an excellent idea" (in response to the first question about the riddle)
npc "what stabbing me is an excellent idea?"
another player "no"
npc "huh ok, are you gonna stab me or what"
same player "no"
npc "ok here it goes, what is two plus two"

Obviously we all know the answer, if a player says something stupid like "I like food" then its wrong and they fail the scenario. If they say something like "42" the npc may deem that that is "close enough" and they pass the scenario.

other tasks could be,
-travel on the bus and get some milk from my old ma...
-warn a npc a boulder is rolling down a hill & he needs to move out the way...
-chat up a grotesque alien hooker (possibly fully equipped with tenticals) for an old, lonely space traveler.
-help the man who asks for help, who will not tell you what he needs help with unless you ask him.

Do you think this would be good fun?

sorry about double post, yes I forgot a fundamental bit, here it is...

You make about 5/10 quests and the players win the game if they pass best 3 out of 5, 6 out of 10 etc.
Players lose otherwise.

is there an edit function on this board? help mods please!

Why not...it worked as a game on "Whose line is it anyway"...?

V

Why the bait and switch, or bother with creating characters you aren't even going to use?  I would think that coming up with your phrases might be fun enough, and even if you knew in advance you were playing the game, there would be enough variety.

There is a game this idea reminds me of, OG, where you play cavemen with VERY limited vocabularies. I think this would make for a fun "one off" game or alternately a session within an established game where the players are cursed (hacked, whatever the game requires) somehow... maybe let them come up with their phrases as needed but once said they are the only ones they can use.

Hmm doesn't really need to be a bait & switch, it useful though because it means the work for making the characters has already been done, the characters can be used for whatever they were intended for afterwards totally ignoring what happened in the game. Reason it's before a game is you can switch/teleport between fun scenarios/realities which may be hard string togather. Reason for needing built characters is they are needed to help people imagine whats happening.

of course it could work as a curse in a game, why not eh?