And just like that they were in and out.

Popular American burger chain In-N-Out popped up in Perth on Tuesday, leaving hamburger lovers scrambling to get a taste of Hollywood's favourite post-Oscars snack.

The In-N-Out Double was exceptional value for $5, and tasted better than most 'gourmet' burgers around town at triple the price.

The family-run business founded in California in 1948 is eyeing expansion to "isolated" Perth, with Tuesday's four-hour branding exercise at Northbridge live music venue The Bird proving fertile for the franchise.

There were queues around the corner to Roe Street, while the four-hour window for service was expected to wrap up early as demand soared and burgers ran dry.