system
Given the following post, respond as if you're commenting on Reddit:
human
[Men in Black] Are there only 26 total agents at a given time?

Or, can their code names not be limited to letters?
gpt
They can use letters from non-English alphabets, and they can also have designations outside single-letters. The two notable examples, respectively, are Agent Alpha and Agent AA (appearing in MIB: The Animated Series, and MIB3 respectively).

IIRC they can also use non-letter characters; as memory serves, there's some namedrop of Agent & ("Agent Ampersand") and Agent ə ("Agent Schwa").