It’s simple supply and demand, really: If your food is so beloved that people will wait outside for a table on the rawest of Seattle nights—backs pressed to the steamed-up storefront to avoid chilly peltings of rain and, subconsciously perhaps, to be a tiny bit closer to the chairs within—why not just open a space next door to harbor more of that cold, wet fan base under a proper roof? Maybe serve them a few drinks while you’re at it?

That’s how the owners of Fonda La Catrina, which serves heartfelt Mexican food to beguiled crowds on Georgetown’s main drag, came to take over the glorified shack next door. Most recently it was a punk club called the Morgue, before that windowless meeting grounds for a motorcycle club. Now it’s El Sirenito, a low-lit compartment of pure white and the occasional rustic wood, its only color coming from the profusion of tequila, mescal, and their sibling agave spirit sotol lining the barback.

Mescal’s recent trendiness means bartenders all over town employ it in cocktails, some marvelous, others not so much. Drinks here skew more to the “marvelous,” ranging from the liquid campfire of El Consuelo (mescal plus the heat of Ancho Reyes chili liqueur) to Agua Dulce, wherein sotol commingles with both lemon and cinnamon—summer and winter by turns.

El Sirenito is a take on a Mexican marisqueria, a casual bar serving snacks of shellfish. The “snacks” part isn’t code for overpriced small plates: Plenty of bites run $3 or $5 apiece; nothing costs more than $10 (incredible given all the fresh local seafood), and you’ll need two or three of them to keep pace with those drinks. The octopus is smoky and remarkably tender; few people go to a cocktail bar for the soup, but the deeply flavored sopa de mariscos is a bowl of Mexican seaside vacation. Everyone freaks out about the bar’s fish tacos—housemade tortillas, juicy fried fish, and an abundance of cabbage and pickled onion and spicy crema, delivering every texture you can think of—and the freak-out is justified.

El Sirenito may be the equation of overflow plus proximate real estate but, in the tradition of some of Seattle’s best next-door sibling bars (Delancey’s Essex, Matt’s in the Market’s Radiator Whiskey), it exhibits the same joyful perfectionism that drew those crowds to Fonda La Catrina in the first place.