Toxic Immunity: Poison Ivy gave Harley a serum that made her immune to the toxins that surrounded their base.
Poison Ivy only secretes deadly toxins when she wants to. Not that it's likely that Harley can be poisoned. Immunity to most if not all organic poisons and drugs is an actual legitimate superpower the Joker has, and Harley was changed by duplicating his origin.
Harley then joined Ivy atop the truck and began to badger Ivy for an answer about why Harley was Ivy's biggest fear. Fine! You want to know what my biggest fear is? Finally allowing myself to count on someone and then having them ditch me.
Toxic Immunity: As a result of Poison Ivy's treatment, she is immune to various assorted toxins and Ivy's own poisonous touch. Enhanced Strength & Stamina: Harley's strength and stamina has been augmented by injections given to her by Poison Ivy.
Weakness: Harley Quinn appears to be fearless, yet she doesn't have enhanced strength, speed, or metahuman powers, making her vulnerable to physical attacks from her more powerful opponents.
Best known as the former girlfriend of the Joker, Harley suffers from multiple personalities, homicidal tendencies, Stockholm syndrome and possibly “shared psychotic disorder.” A survivor of domestic violence (not surprising, given her former beau), she has murdered grown-ups and kids.
Harley Quinn and Poison Ivy are back together, proving themselves as the healthiest superhero couple to come out of Gotham City.
Doctor Pamela Isley is some 40 years older than Harley in publication history, but the two have enjoyed a relationship on any number of levels throughout the 25 years that the Clown Princess of Crime has been smashing hearts with her synonymous mallet.
Harley Quinn season two ends with Harley and Ivy finally accepting their feelings for one another and pursuing a romantic relationship.
Given what we know about the character, despite story nomenclature, the killer kiss is more accurately described as poisonous, not venomous. Regardless, the result is the same. Contact with Ivy's lips delivers a toxin capable of killing the recipient.
In the heat of the moment, Harley and Ivy share an intense kiss. Their romantic feelings for each other sneak up on them—exploring the messy emotions that come along with falling in love. Harley quickly accepts that she has feelings for her best friend—Ivy does not.
In Gotham Adventures #29 Ivy gets physical. She strangles Harley and wrestles with her, and calls her names. She is only barely tolerant of her and her treatment of Harley is as rough as anything we've seen the Joker do - including the name-calling.
Luckily, she did not kill the co-worker she hooked up with, but that was overshadowed by the fact that she cheated on Harley with her (which this comic confirms was cheating, as Harley and Ivy are confirmed to still be “girlfriends”).
She was assigned the undesirable task of taking care of the Joker — an assignment that would change her life forever. In some versions of Harley's origin story, she becomes infatuated with the Joker because he's one of the only few people that seems to actually care for her.
Harley Quinn started gave the Joker the nickname of Mr. J when she was still a pyschiatrist at Arkham Asylum. She also often calls him Puddin.
In 2011's Suicide Squad comic series, Harley Quinn got a new, expanded origin story in which The Joker tosses the psychiatrist, struggling against him, into a vat of acid, which dyed her skin white and also made her insane.
But with both Gotham villains currently headed down different paths of self-discovery in the comics, they quietly called it quits. “Our story…it's not over,” Harley tells a teary Ivy in Harley Quinn #10. “But you need to find your own path, too.
Rose is a Sporeling, a humanoid plant raised as a daughter by Poison Ivy.
They have affectionate nicknames for each other, with Ivy calling her "peanut," and Harley giving her gal a peck under the mistletoe or as she calls it "the kisstletoe." This signifies they're more than just besties, especially as Ivy is adamant about the "no exes" rule.
The Joker does not reciprocate her love and is in fact incapable of romantic emotion as he sees people only as tools to further his own plans. Harley is in denial of this fact and prefers to view him as an antihero until she eventually has to come face-to-face with his complete disregard for her.
Poison Ivy is traditionally portrayed as a seductress who uses her powers to make others do her bidding. But to only see this side of her does a disservice to the character. Ivy is motivated to protect nature against humanity, a crusade that's exacerbated by her suffering from Seasonal Affective Disorder (SAD).
The story "High School Lows" from DC Saved by the Belle Reve #1 (by Tim Seeley, Scott Kolins, John Kalisz, and Wes Abbott) reveals that Harley's worst fear is a truly corrupted Poison Ivy (aka Pamela Isley). Something she doesn't realize is already quietly coming to fruition in the core-DC Universe.