A combination of witty and ditzy used to describe someone who is either smart enough to know how to act dumb or someone so dumb they're actually kind of smart.
Elle Woods is totally witzy.
Someone with a split personality. A Schizophrenic.
Can be as a result of alcohol, drugs or just being Ditzy which is where the rhyming slang comes from.
Look at the state of that guy, he doesnt know if its Good Friday or Christmas Day. He is a Witzy.