Popeye goes into Bluto's diner and tries to order roast duck. However, Wimpy is the waiter, and he tries to mooch everything... especially the hamburgers.
Lou Fleischer provides Wimpy's voice, and yes, he was a relative of Max and Dave: their brother. There was a lot of nepotism in Hollywood at the time; Universal was famous for it under 'Uncle' Carl Laemmle. The Fleischers had brothers-in-laws, nephews, and such on the payroll, but they definitely earned their keep.
As is often the case with the Fleischer cartoons in this period, you had to keep an attentive eye open for all the throwaway gags that Dave instructed his staff to put in.