Here’s a pair of timely knock-knockers for you—one with an eel and the other one with unagi.

Knock, knock.
Who’s there?
Eel.
Eel who?
Eel meet again.

And this unagi one can be as long as an eel!

Knock, knock.
Who’s there?
Unagi.
Unagi who?
Knock, knock.
Who’s there?
Unagi.
Unagi who?
Knock, knock.
Who’s there?
Unagi.
Unagi who?
Knock, knock.
Who’s there?
Unagi.
Unagi who?
Knock, knock.
Who’s there?
Unagi.
Unagi who?
Unagiving up, are you?
(K.T.)

And here’s an extra.

Q: Is this unagi or anago?
A: Anagonna tell you.