Sodium Batman T-Shirt
Holy Alkali Metal!
The Batcave is not only a sanctum-sanctorum for the Batman. It's also a laboratory. Is it any wonder, therefore, that The Dark Knight would celebrate one of the more violently reactive alkali metals in his theme song?
In the periodic table of elements, on the far left side, restlessly sits the alkali-metal series. Their single valence electron is like an armored punch to the face of the elements on the other-side of the periodic table; the halogens. We theorize, therefore, that it's no accident that the lyrics to the theme song of the classic 60's celebration of superhero camp makes no less than sixteen references to Sodium, the second in the alkali-metal series.
At least, in the shortened elemental-symbol version of the Latin-term for Sodium, Natrium. Biff! Pow! Ionize! React! Bond!
16 copies of the element sodium's properties from the periodic table followed by that elusive element Batman on a black, 100% cotton t-shirt.