He's flipped his lid.

4 seconds sound clip from Batman (1966) - Batman Stands Pat (S1E14) TV Series.

You can hear this line at 00:15:58 in the Blu-ray version of the movie.

Quote context

[...]

- Beautiful, beautiful, beautiful!

- Imagine, shearing Batman like a rabbit. Or stretching him into any form I wish. Or shrinking him and sizing him.

- Why, I I'll make him into a sun bonnet. Or a ten gallon hat or a fizz.

- A fizz.... Yes a fizz, I'll dye him red.

- I'll buy myself a camel and go riding off into the desert wearing a tribal chieftain's flowing robes... and Batman on my head.

- He's flipped his lid.

- What're you mumbling about?

- My idle flights of fancy? My little day dreams? Do nothing more than that believe me... I'm a very practical man.

- I already have my 12 jurors' hats and my 12 jurors.

- All I need now.... is Batman's cowl. And the caped crusader out of the way. And my job will be complete.

[...]