Ideally, a whiskey distillery runs like clockwork, every process happening in the same way, day in and day out. Distillers prize consistency—with few exceptions, no one wants their whiskey to end up tasting different from batch to batch.

But occasionally, even at the most scrupulously maintained distillery, things go wrong. Sometimes it’s the result of human error; sometimes it’s pure happenstance. And sometimes it’s because of an experiment or innovation that didn’t turn out as planned. Miles Munroe, master distiller at Westward Whiskey in Portland, Oregon, calls the latter “ugly baby” whiskey.

“It’s something that we thought would go in a certain direction and it didn't,” he explains. “We still love it and it's actually wonderful, but it's not going to be for everybody.”

Although Westward has yet to bottle an ugly baby, Munroe says there are several potential releases that could come out in the future, among them a single malt matured in 100-percent Garryana oak that has notes of “felt pen or model glue” and one matured in an IPA cask that previously held Aviation gin, which he says is “not universally loved.” There’s also a spirit he calls “Centaur” that came about when someone inadvertently blended 4-year-old Westward whiskey with still-strength Aviation gin.

“It’s wild,” Munroe notes, adding that since the accidental blending, Centaur has been maturing for eight years in used casks. Westward is currently restructuring following a declaration of bankruptcy, which Munroe says will allow the distillery to have much more freedom to release non-standard whiskies.

There are probably many more “ugly babies” than we know about, as most distilleries are understandably reluctant to cop to perceived failure. Often barrels that don’t fit the desired profile are sold to brokers or blended out in large-scale batches of a standard product. But there are times that the distillery realizes its mistake may actually be desirable, offering drinkers something unique in flavor, with a great origin story. (Since success is often imitated, however, some “happy accident” stories should be taken with a grain of salt, especially when they sound implausible.)

Munroe says he used to be offended when people asked him what he had screwed up. Then he realized there’s genuine interest in the how and why as a way of better understanding whiskey’s flavor development. “You can learn as much or sometimes more from a mistake than you can from a success,” he says. “We've got to just show everyone. Let's lean into it.”

Balcones Brimstone Resurrection

Only the longest-standing fans of this Waco, Texas distillery will remember this one-off corn whiskey, which was released in 2013 for Balcones’ fifth anniversary. Resurrection came about when founder Chip Tate was distilling Brimstone, one of the distillery’s core whiskies, made from roasted blue corn and smoked over scrub oak post-distillation. The grain solids in the distiller’s beer burned in Balcones’ pot stills, plastering them to the sides so badly that they required a hammer and chisel to get everything out. Rather than discard the spirit, Tate filled it into heavily charred oak and let it mature, bottling the few barrels at cask strength. The familiar Brimstone flavors of sweet smoked barbecue and maple syrup took on a darker, more spiced and herbaceous character, amplified by powerful oak—a remarkable whiskey that can never be repeated.

Wild Turkey Forgiven

Back in 2013, a distillery employee was putting together a batch of bourbon when, somehow, they inadvertently mixed in some rye. Although bourbon-rye blends are now kind of a thing, they definitely weren’t back then. Still, Eddie Russell, associate master distiller at the time, tasted the whiskey and liked it—and the powers that be certainly preferred selling the mix-up to potential alternatives, like distilling it into neutral spirit. Thus Forgiven was born, quickly attracting the attention of bourbon fans (it should be noted that the employee was forgiven as well). A second batch was created intentionally a year later, but Wild Turkey has yet to repeat it again. If you wanted to replicate it yourself, though, the proportions are as follows—78 percent 6-year-old bourbon to 22 percent 4-year-old rye, with the final blend proofed at 91.

Ardbeg Fermutation

Bill Lumsden, the mad scientist distiller who helms Ardbeg, took advantage of an equipment failure at the distillery to make the spirit that would become Fermutation. Faced with a delay in getting the stills running, he could have discarded the actively fermenting wash, which typically spends just a few days in tanks. Instead, he uncovered the tanks for a day to allow wild microbes in and then let the liquid sit for three weeks, fermenting and fermenting some more. The flavors that developed, which carried over into distillation and maturation, were indeed wild for the likes of Ardbeg—lemon sherbet, orange push pop, and no small amount of funk. Lumsden has since initiated other extended wild fermentations on purpose, hoping they’ll yield whisky that’s similarly intriguing and delicious.

New Riff Backsetter Bourbon

This Kentucky craft distillery is well known for its high-quality bourbon and rye, but it also has a playful range of more experimental whiskies. Backsetter is one of those—a peated bourbon that derives its smoky flavors not from the mashbill or barrel, but the backset (solids left over after distillation that get added to the next batch). Adding backset, also called sour mashing, is standard practice in Kentucky, but it’s usually constrained to the same whiskey style—bourbon backset added to bourbon, rye backset to rye, and so on. One day, when New Riff was switching from making peated single malt to bourbon, master distiller Brian Sprance allegedly said, “Fuck it, let her ride,” and added the smoky substance in with the fresh mash. No one knew if it would make a difference to the final flavor—but it did. Even after aging, Backsetter ended up with pleasing char and s’mores notes that meld beautifully with the bourbon’s fruity core.