“Fargo,” Noah Hawley’s crime anthology series on FX, introduced memorable villains in its first two seasons. But in the third, which aired its final episode Wednesday, a different beast emerged. David Thewlis’s turn as V.M. Varga, a bulimic loan shark with decaying teeth and far-right political leanings, has been a hilariously chilling aspect of this season’s exploration of “alternative facts” and magical realism. Reached by telephone in London the day after the British elections, Mr. Thewlis discussed bingeing, purging and politics. Following are edited excerpts from the conversation.

Did you have to decompress, or metaphorically take a shower when filming was done?

I shaved my head. In the last scene, which is a jump of 5 years, we discussed how we’d make Gloria [played by Carrie Coon] and myself look older. That was the last thing we shot of the whole season. I had this idea that we’d thin his hair out and chop into my hair, without going over the top with aging makeup, just to make me look like I’d aged 5 years with the hair. So at the end of that night, I said, “Just shave the lot of it.” As a way of getting rid of Varga. But I kept me teeth.

Was the toothpick in the script, or was that something that you brought to it?

Noah had already come to me with the idea that Varga was purging, bulimic — hence the teeth. When we were doing the camera test, Noah asked someone if they could hand me a toothpick, and instructed me to dig away until the gums were bleeding. I always thought, “Oh, he’s pre-plotting this, and somehow this toothpick’s going to become a weapon in some way before the end of it, or a tool of torture.”

That’s an interesting point: The most violent thing Varga does physically is spray Emmit in the eyes with breath spray.