Ataru's mask: Japanese people wear such masks to protect against dust an pollen in the air, as well as to stop the spread of diseases - both giving and recieving. Sometimes, famous people may wear them as well to conceal their identities, much like Westerners might wear sunglasses. But one thing you can't do normally when wearing one of those masks is eat through one - unless, of course, you're Ataru Moroboshi!
Going Wide: In Japan, missing-person shows often appear on early-morning or mid-afternoon programs called "Wideshows," which are aimed primarily at housewives. If the missing person is important, then it would be major news, worthy of headlines and real news broadcasts, but shows such as these are typically of the tearjerker variety, meant more to evoke sympathy than any real help in finding anyone. This is not meant to trivialize the very real problems of the people involved, however. But shows such as these are more likely to give air time to the average person than the bigger, more serious news programs, because they are constantly looking for any little thing they can make a feature out of.
Manjuu are little cakes made of a sort of pancake-like batter, or sometimes with a rice-cake outside, and filled with bean-jam paste. Sooshiki manjuu (Funeral bean-jam cakes) are differentiated mainly by their black-and-white color. By contrast, red-and-white manjuu represent a happy occasion, such as a wedding. The joke here is that, normally, one tries to entice a missing loved one to come home by promising something special to that person. But sooshiki manjuu are not that big a deal.
Sakura is Cherry's niece. There is also a relationship between their names: Sakura means "cherry blossom," and Sakuramboo means "cherry" (the fruit). Note also that Cherry is a Buddhist monk, and Sakura is a Shinto priestess.
Hakama are large, baggy pants, typically worn over kimono. They are also primarily worn by men. For women to wear them typically requires that the woman be in a profession like Sakura's, or be participating in a graduation ceremony. Female students during the Meiji and Taishoo eras wore them as well.
Stupidity Personified: When Ataru's Mother calls him "the personification of the word 'stupid,'" the word she actually uses, "ikizukuri," refers to a method of serving sashimi. The method involves taking a live fish out of a tank in the restaurant, cutting off its meat while it is still alive, and laying the cuts of meat on the still-twitching head-bones-tail of said fish. Thus, Ataru's Mother means that he is both demonstrating and decorating the very concept of stupidity.
A Yen to Chat: When Ataru says he'll fight Lum as long as his Yen10 coins hold out, he could well mean to put up an extended fight, because for local calls, Yen10 coins used to last three minutes apiece in Japanese telephones. For Yen100, he could stay on the line for thirty minutes, or make ten separate three-minute calls.
Futagoyama is a one-time yokozuna (the top rank in sumo), who retired and became a sumo stablemaster. He is also the uncle of current talented sumo wrestler (and teen-idol) Takanohana, who, as of this writing, may be in line to become the newest yokozuna. Often, he serves as a commentator at sumo contests, much like retired football players and coaches do in the US. Mitsugoyama is a pun on Futagoyama's name (meaning, roughly, "three mountains" rather than "two mountains"). It goes without saying that he's not a scientist, nor does he have any knowledge of Lum and Ataru, so he is the last person one would expect to make a significant comment on the situation.
There's more than one way to shed your skin: When Cherry says he'll try to "skin that cat," what he actually says in the original is "hito hada nugu," which literally means "I'll shed a layer of skin." The idiomatic meaning is "I'll make an effort on your behalf," though Cherry manages to combine both literal and figurative images in this scene.
3-3-7 cadence is used normally for closing ceremonies at a job or a party. Everyone on hand will usually clap together in that cadence: three times, another three times, and then seven times. A variation calls for just one large clap.
Muchi laughs: Ten has fun with homonyms on the word "muchi," which has the usual meaning of "ignorance." He starts off with this conventional meaning by saying that Ataru is ignorant, and that he who is ignorant of his stupidity is also ignorant of his shame. But then he says "Muchi muchi pudding ga suki de," which means "You like muchi muchi pudding." Here, he uses a different meaning of "muchi," or rather, "muchi muchi," to wit, kind of roly-poly, like custard. Then he returns to his previous usage of "muchi" to finish up with "You're the great king of ignorance."
Preview Pun: The yokokuhen (preview) for the next episode (as well as the story itself) contains a take-off on the opening line from Yukiguni, a book by Kawabata Yasunari (1899-1972--suicide), winner of the Nobel Prize for Literature. The line in the original work is, "Tunnel o nukeru to, soko wa yukiguni datta" (At the end of the tunnel was Snow Country). The take-off line is, "Oshiire no nagai tunnel o nukeru to, soko wa yukiguni datcha!" (At the end of a long tunnel in the closet is Snow Country!)
Kappa are mythical Japanese water-dwelling vampires, made famous in a novel of the same name by Akutagawa Ryuunosuke.
The name "Oyuki" means, appropriately enough, "Honorable Snow."
Yukionna (literally, "Snow woman"): A mythical fairy of the snow. She appears where there is an abundant snowfall, dressed all in white, very pale, and kills people.
The Eyes Have It: Me no iro ga kawaru (literally, "the color of his eyes have changed"), generally means that one is excited, angry, or worked up about something. In this case, Shinobu means that Ataru is hot for Oyuki, and his eyes have, in effect, given him away.