Spoilers for Good Omens Season 2 below
Season 2 Episode 4 of Good Omens, "The Hitchhiker," featured a little jaunt back into demon Crowley and angel Aziraphale's World War II era past. We learned, in the first season of the Heaven vs. Hell television show, that Aziraphale, though able to perform miracles, is a truly terrible magician. And yet, in this episode he still manages to wheedle himself some stage time, ready to showcase his magic skills with a famously deadly magic trick.
First performed all the way back in the 1500s, "the bullet catch" trick has a a reputation for being deadly. It doesn't help that the magic shop salesman mentions a "Chinese" magician to whom he sold the trick - magic fans will recognize the reference to Ching Ling Soo (not actually Chinese, but stealing a popular Chinese magician's gimmick). Like the shopkeeper warned, Ching Ling Soo did end up dying from the bullet catch trick when his modified gun malfunctioned. Obviously the whole thing is a bit of a joke setting up the punchline that horrible, horrible magician Aziraphale is in very real danger, especially because a demon named Furfur is blocking the use of miracles. It looks like Aziraphale is set up for a likely death.
And yet. Of course, against all odds, Aziraphale and Crowley end up on top.
Now why is the show's use of this trick such a good representation of Crowley and Aziraphale's relationship? Well, because though they're wholly unsuited for the task ahead of them, but they somehow, despite all odds and probably with an immense amount of luck, are able to make it through. Not only because they trust each other, but also because they're on the same page. Even when Furfur manages to get proof of Crowley and Aziraphale's trust in each other (which he is hoping to use as leverage for a promotion in Hell), dumb luck - and maybe just a little bit of Aziraphale's unlikely sleight of hand skill - is again on Crowley and Aziraphale's side, and they make it out scot free.
It is only when Aziraphale and Crowley find themselves at odds that they end up in real trouble, as we see at the end of the season. As for how they get back on the same page again? We'll simply have to wait for season 3 to see.
**For those interested in how the bullet catch trick is performed nowadays... though Aziraphale instructs Crowley to "Aim at my mouth, but shoot past my ear," the trick is no longer performed with live rounds, as you might, well, shoot someone. There are different ways of performing the trick, including with the shooting of blanks or of hot wax, with the bullet hidden already in the mouth.