Agent 257 is a television character that appeared in "Episode 257-494". He is a reference to James Bond.
A short footage of the secret agent was seen during the Teen Titans' search for Control Freak in Cook's Electronics, where the agent is shown fighting off-camera enemies on top of the Eiffel Tower in Paris, before jumping off the tower and flying away on a glider.
Later, when the Titans and Control Freak went into a cat-and-mouse chase in the TV dimension, the agent was seen again with a Renaldi Device, but quickly lost possession when Control Freak bumped onto him. The agent was eventually stripped of his tuxedo and laser watch by Control Freak, who decided to use the devices for himself.