The lesson here is 'Buy your own razors'.
James McAvoy is mostly known for his roles in 'The Last King of Scotland', 'Atonement', 'Split' and the X-Men franchise, and would probably be talked about in good terms by everyone who's seen his work.
That is until he told this story about shaving his nether regions to Stephen Colbert, and now will forevermore be known as "THAT James McAvoy, with the razor story".
We understand why he kept this one to himself for so long.
