One of the main characters in the "Peanuts" comic strip by Charles M. Schulz. His older sister is Lucy, and his baby brother is Rerun.
Linus is an amazingly well-read person, especially considering that he's probably only five years old. He can quote passages from the Bible and seems to have a solid grounding in general philosophy and theology. Despite his grown-up way of thinking, however, he is still just five years old. He sucks his thumb, drags a fuzzy blue security blanket around with him everywhere he goes, and must endure much abuse from Lucy, who, besides being a big sister, is also crabby and a fussbudget. He is much beloved by Charlie Brown's little sister Sally, who calls him her "Sweet Baboo" -- Linus, however, has no interest in love and tries to ignore her.
About that blanket: Did you know Linus (or at least his creator, Sparky Schulz) actually invented the term "security blanket"? Linus was rarely seen without his trusty blanket. He dragged it on the ground behind him, he cradled it next to his head while he dozed off (always sitting up, always with his thumb stuck into his mouth), and he even wielded it as a tool and a weapon: he could snap people with it like a wet towel, he could use it to snag something off a high shelf, and he could use it as a disguise. Nobody could fashion a shepherd's headdress from a baby blanket the way Linus could! The blanket was also useful for throwing over his head whenever Sally had showered him with too much gushy love talk. But the blanket could also be used as a weapon against Linus -- Charlie Brown's beagle Snoopy loved to stalk Linus, grab his blanket, and go tearing all over the countryside with it; Linus, who never let go of the blanket, got dragged along with it.
Linus is one of the few people who really understands the true meaning of Christmas, and he can be found every Halloween waiting in a pumpkin patch for the Great Pumpkin, who flies all over the world bringing candy and presents to all the good children who believe in him. Every year, he is disappointed, but he never loses faith; clearly, the Great Pumpkin is just waiting for Linus to find a pumpkin patch that has the proper sincerity...