Though this episode was the last of the original series to be aired, the final episode of the original series to be produced was Batgirl Returns (1994).
The Lion and the Unicorn are the supporters of the Royal Coat of Arms of the United Kingdom. It is an analogue for Great Britain that has been used in a nursery rhyme; Alfred's part of the code is the first two lines of the song.
Struggling against the truth serum, Alfred quotes the opening lines of The Brook and later on The Charge of the Light Brigade, both by his namesake, Alfred Lord Tennyson.
The short and tall thugs who initially greet Alfred in London are named "Bert" and "Ernie," after the Sesame Street (1969) characters.
Final appearance of Red Claw in the DCAU. It is not made clear if she drowned in the River Thames or was captured and imprisoned, though the former appears more likely as she is not seen or heard from again.