John C. Reilly as Dr. Steve Brule. Photo: Adult Swim

From Matthew McConaughey to Rachel McAdams, John Travolta to Jessica Lange, Terrence Howard to Taraji P. Henson, acclaimed actors who travel to television from the big screen tend to bring a lot of attendant hoopla with them — provided their shows air in prime-time, apparently. That’s the only reason I can think of that Tony- and Oscar-nominee John C. Reilly isn’t regularly showered in praise for what he’s been doing on late-night ratings powerhouse Adult Swim on a weekly basis this summer. The star of films ranging from Talladega Nights to We Need to Talk About Kevin, Reilly is anchoring the fourth season of Check It Out! With Dr. Steve Brule, the bizarre local-news parody from co-creators Tim Heidecker and Eric Wareheim. (The season finale airs tonight at 12:15 a.m.) Reprising a role he developed over five seasons of the pair’s Tim and Eric Awesome Show, Great Job!, he plays Dr. Steve, the semi-functional host of a disastrous human-interest show. And word to the wise, he’s delivering one of the best comedic performances on TV.

It starts with the character’s look. Reilly’s physical appearance has always served him well as an actor. There’s something about the combination of his large frame and round, expressive face that makes him look not so much tall as overgrown, like a child stretched to adult proportions. This gives him an air of vulnerability that belies his size; it lends pathos to his dramatic performances, like the sad-sack cop in Magnolia, and a goofball naïveté to his comedic turns, like the fake music legend in Walk Hard: The Dewey Cox Story. It’s how a guy who’s six-foot-two can sing the ode to interpersonal invisibility “Mr. Cellophane” in the film adaptation of Chicago and earn an Oscar nomination, or pair up with the relatively diminutive Mark Wahlberg in Boogie Nights and come across like a natural sidekick.

In these strictly physical terms alone, Dr. Steve is his magnum opus, the idiot man-child he was born to play. Wearing a brown suit that’s at least two sizes too small, teasing his curly hair to fright-wig proportions, twisting his mouth and squinting his eyes to give his face a vibe of permanent confusion, Reilly leans into his quirks as Dr. Steve.

It’s the sort of role that demands slapstick with an almost Newtonian certainty, and Reilly never fails to rise, or more accurately fall, to the occasion. Dr. Steve stomps, lurches, and bumbles through every segment; even something as simple as standing still and introducing his latest topic can end in physical havoc, with smashed props and toppled glass-brick sets. This being a Tim and Eric production, the pratfalls often stretch into cringe-comedy territory. In last week’s episode alone, Brule tripped on the way to the soundstage and cut his head so badly that his producer stapled the wound shut on camera; he got hit hard enough in the head with a baseball bat during a piñata stunt gone wrong that he vomited from the impact. For a performer equally at home in absurd Judd Apatow comedies and painful Paul Thomas Anderson dramas, the blend of funny-ha-ha and funny-yikes is ideal.

But it’s the sense that you’re watching a toddler in the body of a large middle-aged man that gives Reilly/Brule his best material. Dr. Steve greets his topics — space, friends, cars, music, eggs — with appropriately childlike wonder and delight, his twinkling eyes and introductory shout of “Let’s check it out!” evoking Christmas-morning levels of enthusiasm. He reacts to his guests with a complete lack of guile, whether holding their hands and kissing them on the head or announcing their physical flaws to the world like a child ignoring his mother’s advice that it’s impolite to point. He’ll eat anything put within range of his mouth, from seafood out of a dumpster to MDMA offered by a strip-club owner. The result is often gross-out body-fluid humor that Reilly throws himself into with terrifying commitment; the scene in which he “had to go to the bathroom at both ends” after having too much to drink at a leather bar he mistook for a Hell’s Angels hangout is the ne plus ultra of the genre. When he gets hurt, insulted, excluded, or frightened, he cries, sulks, panics, and screams so convincingly you want to go get his parents. (Unfortunately, his mother, Dorris Pringle-Brule-Salahari, is an abusive murderer who kept him caged in the basement as a boy after his fry-cook father skipped town, so that rules that out.)

Then there’s his voice, a masterful mangling of pronunciation and grammar that’s the character’s trademark. Back when Brule was a recurring character on Awesome Show, Reilly played him relatively straight, sounding simply dopey rather than deranged. Once he became the star of his own series, however, his speech pattern took a turn for the weird. He adds unnecessary “r”s to the opening consonants of words: “boats” becomes “broats,” “pirate” becomes “prirate,” “puppets” becomes “pruppets,” and so on. (The bit during an episode on fear where he popped out from behind the set and shouted “Broo!” may be the series’ funniest moment.) He’s incapable of properly pronouncing anyone’s name, and he’s often not even in the ballpark; those that begin with “D” are especially taxing on him for some reason, and Davids, Dans, and Dons are invariably mangled into something like Dang or Dong or Drungus. The preposition “of” gets a real workout, most memorably when the Doctor discovers that when it comes to American currency, “one of paper equals four of coin.” And there’s a mushmouthed quality to his voice throughout, as if he’d been suddenly awoken from a nap just before the camera started rolling. (The overall effect is so strange and singular that it defuses criticism that the character is some sort of mean-spirited ableist stereotype: No real person on Earth sounds like this.)

And as ill at ease as Brule appears in his man-on-the-street segments, he fits right in to the peculiar public-access world Heidecker and Wareheim have built around him. The VHS-distortion effects, the no-budget graphics and set design, the cast of non-actors playing Brule’s fellow Channel 5 employees, the occasional eruptions of Mulholland Drive–level menace amid the ridiculousness: Dr. Steve’s solo show is the Tim & Eric aesthetic in its purest form, at a time when the pair’s other ventures (notably their bigger-budget recent series Bedtime Stories) have largely moved away from the deliberately crude, visually noisy look that once defined them. As Reilly’s collaborators, they seem determined to rise to his level of calculated madness. I don’t think it’s an exaggeration to compare this relationship to Sam Esmail and Rami Malek on Mr. Robot or Bryan Fuller and Mads Mikkelsen on Hannibal, in the sense that the look and work of the performer enables the filmmaker to take things farther than they otherwise could. That’s the mark of a great performance, no matter how odd it looks, or how late you have to stay up to see it.