FD-27 is one of the more misunderstood sheets in the early Family Dog catalog: a Mouse and Kelley poster of arresting design, printed to advertise a Howlin' Wolf headline at the Avalon with Big Brother & the Holding Company on September 23–24, 1966. The poster is famous among collectors, and a persistent story attached to it holds that the shows were cancelled and never happened. That story is wrong. The primary record — the Ross Hannan / Corry Arnold per-venue show list, corroborated by the recollection of Big Brother's own guitarist Sam Andrew — is clear that the Avalon weekend went ahead: Howlin' Wolf cancelled, and Big Brother headlined in his place, with Unquenchable Thirst (a group carrying ex–Grass Roots members) added to fill out the bill. What the FD-27 poster preserves, then, is the originally advertised bill that was superseded, not a phantom event that the calendar erased.

The distinction matters, because the "cancelled show" framing is largely a creature of the poster market. Nearly every dealer listing — Heritage, Bonhams, Recordmecca, and others — repeats that "the concert was cancelled," language that inflates the scarcity and mystique of the sheet. But that is sales copy, not a show record, and it does not survive against the primary sources. The shows happened; Wolf was the one who did not appear.

The headliner who was advertised was Chester Burnett — Howlin' Wolf — sixty-one in 1966, still recording for Chess, still touring hard. His booking is part of what makes the poster matter even though he pulled out: Chet Helms, who ran the Family Dog at the Avalon, was deliberately wiring the Chicago electric blues lineage into the new San Francisco scene, the way Bill Graham was doing simultaneously across town at the Fillmore. The Avalon had hosted Lightnin' Hopkins in August; the fall of 1966 was the season when blues elders were placed in front of audiences raised on folk and psychedelia. A dealer superlative that FD-27 is "the only Family Dog poster silk-screened in advance of its show" circulates in this same market copy; it rests on a single source and is recorded here as an unverified claim, not a fact.

The band that actually headlined is the other half of the story. Big Brother & the Holding Company, with Janis Joplin out front — she had joined in early June 1966, some three months earlier — was the Avalon's house attraction in the making, and by late September was on the run that would lead to Monterey Pop the following June. So the weekend that survives is not the Wolf/Joplin summit the poster promised, but a genuine Big Brother headline at the Avalon, with a substitute act rounding out the bill.

What FD-27 documents, then, is a substitution, not an absence — and a small lesson in reading the artifacts. The Mouse and Kelley sheet is a beautiful record of an intention: Chet Helms's plan, in late September 1966, to put Howlin' Wolf at the top of an Avalon bill. Wolf's cancellation changed who played; it did not empty the room. The poster outlived the plan the way a printed program outlives a last-minute cast change — the names on the paper and the names on the stage no longer quite match, and the honest record is the one that says so.