Darkwing already had the ratcatcher prior to him meeting Launchpad and getting the Thunderquack
In appearance, it is similar to Judge Dredd's Lawmaster
, which also has its hero's emblem on the front. It is also similar to Batman's aray of vehicles which all bear his bat.
In one apearence
, we are shown that Darkwing also has a River Ratcatcher, which he can use on St. Canard