Is Dr. Michio Kaku crazy

I wouldn't say he's crazy. I would say he's exceptionally bad at outreach because he cheerfully takes any opportunity to appear on TV that he can get, even if they're pseudoscience or anti-science venues. As such, he opens himself up to being taken out of context.

Crazy? Maybe yes, maybe no.

Deluded? Certainly.

A whacko? No doubt!

Makes you wonder which mail-order university awarded him a PhD . . .

He a showman, selling popular science talk in exchange for money. His Ph.D. is real. But he goes a bit too far with the popularizing.

Likely no more crazy than the average human. He knows most of us humans prefer violence death, spectacular to reality so he taints his science to make it more interesting. Neil

He is just like Richard Dawkins. Using science as a tool for his own personal agenda. That is disgusting.

Crazy sexy? Yes I do.

He's an attention junkie and he gets carried away with trying to impress people with lots of exaggerated hyperbole in order to make people say "Wow!" If Fox TV want somebody to wave their arms about and say how solar flares can be devastating (without happening to mention the low probability of such events) then he's their man.
He also makes appearances on that haven of conspiracy tomfoolery Coast To Coast AM. I've heard him talk about the possibility of an impact from the asteroid Apophis in 2036 where he talks about it being deflected by the Earth's atmosphere at 29,000 km distance (completely wrong) and creating a tsunami 'several miles high' (physically impossible).
I've heard of him being described as a borderline crank. He's certainly the darling of the doomsday crowd who quote some of his wilder flights of fancy as coming from a 'real scientist'.

I would not want to get into an argument with Dr Kaku on the subjects of cosmology or astronomy or physics. He knows far more than I do in any of those particular disciplines. However, my perception is that he has taken an opportunity to build a bridge of communication into a soap box for monetary gain. He may be trying to emulate Dr Bronowski and Dr Sagan, but he is cashing in on the fears of his audience, as indeed Dr Sagan did in the last few years of his life (ref. Parade magazine articles on Nuclear Winter, his international political views buried within the pages of his books, etc). This method, in my opinion, does little to promote science, and instead tends to encourage the internet conspiracy whack jobs and the political extremists. I personally view his recent popularized accounts with a jaundiced and skeptical eye.