Jerry Bails' Finger in Every Plot from CAPA-Alpha #12 (September 1965)

This is what propted Bob Kane's letter in Batmania #17.

Biljo White's Batmania 11-15

Biljo was one of early comics fandom's most active fan writers and artists. Beginning with Komix Illustrated in 1962, living in Columbia, Missouri, by the name of Bill J. White. Just about everyone called him Biljo or Capt. Biljo.
Biljo was a huge influence on early fandom and well known by all involved in it in the 50s, 60s, and 70s. Other accomplishments include being co-creator of “The Eye”, creator of “The Fog”, Art Director of fanzine Alter Ego, as well as publisher of The Comiccollector for a time, and The Stripper, a magazine for fans of comic strips.He drew many such strips but his most famous was The Eye, a freakish crimefighter with an eyeball for a head, much weirder than any evil-doer he ever vanquished.

Biljo White's Batmania 6-10

From wiki:
Batmania had the tacit approval of DC, after White sent a copy of his first issue to renowned fan-friendly editor Julius Schwartz, who liked it, and even gave it a plug in the pages of Batman #169, causing the membership of the fledgling "Batmanians" group to grow "nearly 1,000-strong". The first issue was in such demand that White:
"kept printing up more and more copies, until the ditto masters gave out — and I still couldn't satisfy all the requests. It convinced me more than ever that there was a large body of fans who enjoyed the adventures of Batman and Robin as much as I did.
Batmania became the unofficial "fanzine for Batman fans. Appearing under the motto "For Batman, we accept nothing as impossible," It was released a year after sales on the two Batman titles — Batman and Detective Comics (DC Comics) — had "dipped alarmingly."

Biljo White's Batmania 1-5/1964

Biljo White had a block building out back of his house that in it's glory days, was filled with more Golden Age comics that you could imagine.
Full runs.
Key issues.
The 'White House of Comics' it was called.
Roy Thomas would use the comics Biljo owned for research when doing articles, including his contribution to Xero.
But Batman was his favorite. So much so, that in addition to creating many characters of his own and publishing them in various 'zines (plus becoming art director for Alter Ego with Roy Thomas) he decided to put out a little ditty called 'Batmania'. As far as I know, he coined the phrase basing it on the then-rampant Beatlemania. It was a natural fit.
He also produced a 'Bat-Bulletin' to update subscribers in between issues. He had an extremely amiable personality and wonderful whimsical art style that made for good copy and it became a huge success.
A few issues came out after Biljo's tenure including a 'Neo-Batmania'