In the DC Extended Universe film Suicide Squad, flashbacks show Joker convinced Harley Quinn to bath in the same chemicals as he did. After their break up, a drunken Harley blew up Ace in Birds of Prey.
The DC Extended Universe film Suicide Squad features flashbacks showing Joker lured Harley Quinn into bathing in the same chemicals he employed. After they parted ways, a drunk Harley inadvertently blew up Ace in Birds of Prey.