The actor sat down on "The Ellen Degeneres Show" Monday where she retold the story while playing Ellen's "Celebrity Confession" game.
"I was doing my first American film back in 2000 and there was a sex scene in it. I had never done a sex scene before. I went up to the director Joel Schumacher in just a dressing gown and nothing underneath. I opened it up to him and referred to it as a retro bush. I decided I would go trim it."
Farrell said he asked the hair and makeup team on set if anyone had a beard trimmer that he could use, and that's when he went on to trim the bush.
"I went to my trailer and sat over a bin. I trimmed the right side a little bit, then obviously had to match it and trimmed the left, but overshot the mark a little bit. Had to get back in, approach the right again, overshot that," he said.
"At this stage I was sweating. Went back in and re approached the landing strip on the left, then I looked down and had a little landing strip. Lovely little landing strip."
Farell is promoting his upcoming film "The Beguilded" and is also celebrating 10 years of soberiety. The actor told Ellen about the personal milestone, saying he enjoys the progression of his life, specifically the getting older part.
"I love getting older," said Farrell. "Except getting hair in strange places and losing hair in not-so-strange places a bit. It's kind of an aversion that's unfavorable."