Poor Rudolph grew up ostracized for his glowing red schnoz; like children, the reindeer in the classic Christmas story made fun of Rudolph for being different and abnormal. Turns out he wasn't that weird, or at least not the only reindeer to ever be born with a red nose. Smithsonian Mag posted a study from researchers in Norway and the Netherlands about a sliver of the reindeer population who do, in reality, have reddish noses.
Alas, these red noses don't glow in the dark. But the scientific explanation is pretty cool, anyway. The researchers found that some reindeer have red noses due to densely packed blood vessels at the tips of their snouts. Their Christmas-themed explanation:
"The nasal microcirculation of reindeer is richly vascularised, with a vascular density 25% higher than that in humans. These results highlight the intrinsic physiological properties of Rudolph’s legendary luminous red nose, which help to protect it from freezing during sleigh rides and to regulate the temperature of the reindeer’s brain, factors essential for flying reindeer pulling Santa Claus’s sleigh under extreme temperatures."
They found that the reindeer's nose was one of the hottest points on its body after exercise, proving that it's a key body part for temperature regulation. The study unfortunately didn't go into why only a fraction of reindeer get into the Christmas spirit--black noses are, of course, far more common. Some noses must just be better than others.