Batman

I was surprised to read that Chad & Jeremy were a real group.  In this episode they performed Distant Shores and Teen-Age Failure.

Sir Sterling's butler is called Rhet (Rhet Butler from Gone with the Wind).

From archived tv.com page:

Burgess Meredith developed the Penguin's "quack" to cover up coughing brought on from having to smoke cigarettes again after he had given up doing so nearly 20 years before. Just before he says, "In the immortal words of Emil Zola," Meredith coughs and quickly covers it up with a "quack."

This is the last episode in which the Part 2 teaser sequence features stop-motion clips of events from the previous evening's episode; from the next episode on, the teaser in Part 2 will immediately pick up where the previous episode left off.

From archived tv.com: 

Adapted from a comic book story in Batman #36 (August/September 1946), with the same title as episode #61, written by Alvin Schwartz.

Ted Cassidy makes an uncredited cameo appearance as Lurch from The Addams Family which aired on ABC from 1964-66.