Waiting for the opening applause to die down after he takes the stage for the first of two shows on Friday night at the Chicago Theatre, comedian Jim Gaffigan — currently making the rounds on his “The Noble Ape” tour through April of next year — smiles and thanks the audience for that kind introduction, adding as a bashful aside, “You’re making me feel only 20 pounds overweight.” And within seconds of grabbing the microphone to start his 70-minute show, the internationally touring headliner is off on a series of self-deprecating bits about his weight, his beard (a woolly new addition to his familiar look) and his lack of deep knowledge about basically anything. Gaffigan — who has written two best-selling books, recorded five hourlong comedy specials, starred in a sitcom with his name in the title and earned two Grammy nominations — is a bona fide expert at describing his entire life from a bemusedly concerned distance, as if it is something constantly (and more often than not, troublingly) beyond his control, a series of events happening to and around him, rather than a thing he is actively participating in. Remarkably, his career accomplishments — and the fact that he has five kids — haven’t diminished his ability to convincingly play the bumbling American everyman. In fact, they’ve only heightened the divide between man and comedian, clearly showcasing both his dedication to the craft and the level of talent he’s working with to be able to deliver nonstop one-liners and observations one after another with seamlessly smooth transitions while portraying a witless slob. His shtick — and it’s a good one — is that he is a useless doofus with a one-track mind, self-centered, cocksure and always ready to eat. Essentially, he is a live-action Homer Simpson. “I look the same whether I’m wearing a T-shirt or a tux,” he says, slightly miffed but with just a hint of pride. “I look like someone who eats fast food.” And in red Adidas sneakers and a black button-up shirt about a half size too small, tucked into gray pants with a cinched-tight black belt, he nails the part. “I’m kind of obsessed with not being into fashion,” he confesses when discussing his outfit choice and