How do you make a "Name that Character" obby?

First of all. Never put random tags onto your question. Your question does not involve animations, cframe, guis, or even the RbxLibrary..

You need a part and a script. Put the script into the part.

function Chat(m)
    if m=="WordHere" then
        script.Parent.CanCollide=false
        script.Parent.Transparency=.5
        wait(4)
        script.Parent.CanCollide=true
        script.Parent.Transparency=0
    end
end
all=game.Players:getChildren()
for a=1,#all do
    all[a].Chatted:connect(Chat)
end
game.Players.PlayerAdded:connect(function(p)
    p.Chatted:connect(Chat)
end)