During the clubs' occasionally toxic rivalry between 1997 and 2005, Keane and Vieira enjoyed some visceral battles on the pitch and in the tunnel, as their sides fought for supremacy in the Premier League.
Both players left English football within five months of each other in 2005, and Arsenal-United fixtures have become tame affairs since, which makes ITV4's documentary on the pair tonight a nostalgic treat.
Although still prone to pouring petrol onto the fire, Keane has mellowed in his post-playing career. He has shared company with Vieira before with ITV, when once he wore the expression of a man itching to have it out with the Frenchman inside Highbury's marble halls.
When it comes to selecting their all-time XI, naturally, they didn't always agree. It's a squad of 12, since neither would back down over one position, including the pair of them.
There is no Gary Neville, David Beckham, no Ryan Giggs and no Paul Scholes, so who makes the cut?