Theron puckered up to pay homage to her heroine at the Premiere Icon party on Tuesday night (20SEP05) and stepped down from the stage to plant her lips on MacLaine's posterior.
A red-faced Theron blamed her show-stopping tribute on the painkillers she was taking to combat an aching neck.
She says, "It was a combination of my painkillers and the fact that everybody was paying tribute to this incredible woman, this incredible actress, so I had to go to the physical aspect of kissing her a**."
Theron, who was honoured alongside MacLaine and Lindsay Lohan at the Hollywood bash, admits she was amused with her heroine's response: "She loved it. She said it was the best she's had all year."
And thrilled MacLaine suggested the odd act made her realise she needs to hang out with Theron.
She states, "I've gotta get to know her... I should get drunk with her."