Confirmed to be in the King of the Hill universe. Emily Spivey asked Mike Judge, creator of King of the Hill, for permission to use Mega Lo Mart in the show and he said yes.
The character of Betty Hart is based on creator Emily Spivey's mother. Betty's voice actor, Maya Rudolph, shared an office with Spivey on SNL and often heard her mother's voice through voice mails so she had a direct model from which to base her impression.
The pilot episode "Can't Get There from Here" was not the first aired, but rather the second.
Several of the show's writers voice characters on the show. Rich Blomquist voices Daniel Culp, Andy Bobrow voices Bud, Christy Stratton voices Dawn, Jeremy Rowley voices Jimmy Lee and voiced Mayor Webb before the role was recast with Jon Hamm during the second season, and series creator Emily Spivey voices Louise Culp.