"Old Sweepy" was an undercover Dai Li agent who kept an eye on the Lower Ring of Ba Sing Se, where he spread misinformation wherever and whenever Long Feng desired. To maintain his cover, he let people believe he was a normal, talkative, old janitor.
Old Sweepy originally worked in the Upper Ring with the top officers of the cultural authority but was moved by Long Feng into deep cover as a menial laborer after a botched assignment.
In 100 AG, he was visited in his warehouse by Team Avatar and Jet, during their search for information regarding Appa's whereabouts. After Aang discovered a clump of his flying bison's white fur in the abandoned building, Old Sweepy informed them that they had shipped Appa off to Whaletail Island the previous day. This turned out to be false, however, as Old Sweepy hoped to earn his way back into Long Feng's good graces by leading the team out of Ba Sing Se.
Old Sweepy claims to have not had a vacation in years.
Even though Toph was usually able to tell when someone was lying, Old Sweepy was able to spread false information in regards to Appa's whereabouts in her presence without her sensing it. This makes him the first person to do so, the second being Azula during the Day of Black Sun.