Power Girl crashes from outer space right in front of Harley Quinn. Harley then decides to haul her back to her apartment to recover. When it is made clear that Power Girl has temporarily lost her memory, Harley decides to strip her and stuff her into a new costume, intending to turn the amnesiac heroine into her own sidekick.
Fun fact, Harley would get a chance to strip another DC bombshell two years later: https://sleepycomics.com/8589
A two for two win for Harley. Here's hoping she gets a third!