The actor caused a stir at the Berlin Film Festival when he paired a smart suit with a cut-put paper bag that read 'I am not famous anymore', a line he has been tweeting daily since 13 January.
CLICK ON PHOTOS FOR GALLERY
Shia was joined at the world premiere of Nymphomaniac by his co-stars, including Stellan Skarsgard, Uma Thurman and Christian Slater. But it was the 27-year-old who stole the show with his unusual behaviour.
His arrival at the screening followed an equally bizarre display at the film's press conference that same evening.
Making a statement: Shia attended the Nymphomaniac premiere with a paper bag on his head
Sporting a dishevelled appearance - including a shaved-down tooth - for the cast panel, Shia answered just one question before quickly exiting the room.
Asked how it felt to be in a film with such explicit sex scenes, he took a sip of water before replying, "When the seagulls follow the trawler, it's because they think sardines will be thrown into the sea."
He then thanked the audience, got up and left.
It came hours after a bizarre appearance at the film's press conference
It was seemingly a reference to a famous incident involving football star Eric Cantona, who spoke the exact same quote prior to walking out of a press conference in 1995.
His co-stars looked stunned by his sudden departure, but quickly recovered. "Obviously, the script is packed with a lot of sardines," joked Christian. "One sardine after another."
The actor answered just one question before leaving - much to his co-stars' amusement
The weekend capped a month of odd behaviour from the Transformers star, who also reportedly lunged at three men who tried to take his picture on Saturday night.
Shia was recently involved in a fight at a London pub, and in January was involved in a plagiarism scandal with author Daniel Clowes, to who he later apologised, tweeting that he was retiring from all public life.