So, Christian Bale and Ben Affleck bump into each other in the Batman aisle of a Los Angeles costume shop…

It sounds like the beginning of a bad joke, but a surprise encounter between Hollywood’s incumbent Batman and his successor was revealed at this year’s Comic Con in San Diego.

Affleck was appearing at the huge fan convention to promote Batman v Superman: Dawn of Justice in which he makes his first appearance as the caped crusader ahead of an upcoming standalone Batman movie which he will both star in and direct.

In conversation with director Zack Snyder – who incidentally declared Affleck “perfect” as “an older, burned out…at the end of his rope” Bruce Wayne – the Argo Oscar-winner, 42, revealed he was given an important piece of advice by Bale, who played the lead in Christopher Nolan’s Dark Knight trilogy.

Ben Affleck stars as Batman in Zak Snyder's Batman v Superman: Dawn of Justice (IMDB)

Christian Bale as Batman in a scene from 2012's The Dark Knight Rises (AP)

"Before we started the movie I was getting my kid a Halloween costume. My son is really into Batman," Affleck told the Comic Con audience according to the BBC.

"We went to a costume store in Los Angeles... it was pretty empty. And I was in the aisle and I heard this 'Oi!', and I turned around, and it's Christian Bale!

"And there he and I were, standing in the Batman section."

"I said, 'Do you have any tips?'," an apparently awestruck Affleck asked. Bale’s answer? “Make sure you can piss in that suit."

Affleck hastily added that Bale was also buying a costume for his son: "He doesn't just hang out [in the Batman aisle]".

Batman has previously been played by Michael Keaton, Val Kilmer and George Clooney but fans feel very strongly about who can and can’t play their superhero.

A petition calling for Affleck to removed as Batman/Bruce Wayne claiming he “won’t do the role justice” has been signed by more than 97,000.

In pictures: Comic-Con 2015 Show all 30 1 /30 In pictures: Comic-Con 2015 In pictures: Comic-Con 2015 Comic-Con 2015 Co-hosts/actors Bella Thorne (L) and Tyler Posey perform onstage during the MTV Fandom Fest San Diego Comic-Con at PETCO Park In pictures: Comic-Con 2015 Comic-Con 2015 Executive producer/creator Bryan Fuller waves as he arrives at the 'Hannibal' Savor the Hunt panel during Comic-Con International 2015 Getty Images In pictures: Comic-Con 2015 Comic-Con 2015 Actor Ron Perlman poses for a portrait with Ron Perlman impersonators at Comic-Con International 2015 in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Cosplay enthusiasts Jonathan Michael (L) and Connor Breen are dressed like the Mad Hatter from "Alice in Wonderland" during the 2015 Comic-Con International Convention in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Guests attend the Dragon Ball Z: Resurrection 'F' San Diego Comic-Con opening night VIP party held at Whiskey Girl in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Actor Denis Leary speaks on stage at the FX TV Block featuring 'Sex&Drugs&Rock&Roll,' 'The Strain,' and a sneak peek of 'The Bastard Executioner' panel during Comic-Con International 2015 Getty Images In pictures: Comic-Con 2015 Comic-Con 2015 Actor Greg Grunberg (left) and writer/producer Tim Kring take a selfie on stage at the 'Heroes Reborn' exclusive extended trailer and panel during Comic-Con International 2015 Getty Images In pictures: Comic-Con 2015 Comic-Con 2015 Actress Lea Michele walks onstage at the 'American Horror Story' and 'Scream Queens' panel during Comic-Con International 2015 Getty Images In pictures: Comic-Con 2015 Comic-Con 2015 Actresses Emma Roberts (L) and Lea Michele of the show 'Scream Queens' visit the Scream Queens Mega Drop Ride during Comic-Con International 2015 Getty Images In pictures: Comic-Con 2015 Comic-Con 2015 (L-R) Actors Liam Hemsworth, Josh Hutcherson, Jennifer Lawrence and director Francis Lawrence of "The Hunger Games: Mockingjay - Part 2" attends the Lionsgate press room during Comic-Con International 2015 at the Hilton Bayfront in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Actor Jeffrey Dean Morgan and actress Halle Berry speak onstage during CBS TV Studios' panel for "Extant" during Comic-Con International 2015 at the San Diego Convention Center In pictures: Comic-Con 2015 Comic-Con 2015 Cosplayers pose for pictures while a picketer holds a pro-religion sign outside of the Convention Center at the 2015 Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Brandon Moriesta (R) interacts with a Cosplay character at the 2015 Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 A group of Power Rangers pose inside the Convnetion Center at the 2015 Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 A person who goes by the name of Nomad poses for a photo during the 2015 Comic-Con International Convention in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Lee Shannon, dressed as Ming the Merciless, and his girlfriend Kira Krend, of Kaneohe, Hawaii, chat on the escalator at Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Fans wear costumes at the convention center on opening day of the 2015 Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Attendee Jerry Lee holds up his baby Dylan Lee, seven months, between Lego figures of Iron Man and The Hulk at Comic Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Dustin Agosta, whose drag name is Discord Adams, is dressed as a drag Joker at Comic Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Young attendees look at a figure of a zombie from "The Walking Dead" television show at Comic Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Ayelet Bick takes a photograph of herself next to a Star Wars figureat Comic-Con 2015 in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Super heroes on display at the Comic-Con in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 An attendee dressed in cosplay as the character Ash from the movie "The Evil Dead" outside the 2015 Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Ronnie Nadal poses for a photograph with his two daughters, Kalissa, 9, and Kailah, 6, at Comic-Con 2015 in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 Sabastian and Julia Sanzberro, dressed as Fred Flinstone and Barney Rubble, walk the trade floor at the 2015 Comic-Con International in San Diego In pictures: Comic-Con 2015 Comic-Con 2015 People dressed as sharks dance outside the San Diego Convention In pictures: Comic-Con 2015 Comic-Con 2015 Participants dressed in Zombie outfits walk down the Gaslamp Quarter outside of the 2015 Comic-Con International in San Diego, In pictures: Comic-Con 2015 Comic-Con 2015 A dressed participant at Comic-Con International in San Diego Convention Center In pictures: Comic-Con 2015 Comic-Con 2015 Dressed participants at Comic-Con International in San Diego Convention Center In pictures: Comic-Con 2015 Comic-Con 2015 Participants pose for the photograph at the Comic-Con International 2015 in San Diego

During Comic Con Affleck admitted to nerves about taking on the role – especially considering his widely derided last outing as a superhero in 2003 film Daredevil.