- Channel Hop: Twice; the series moved to Weekly Shonen King from 1972 to 1973, then to Comic BonBon from 1987 to 1990.
- Colbert Bump: With the overwhelming success of Sequel Series Osomatsu-san, ebook sales for the original series have gone through the roof, selling over a million copies by the beginning of -San's second cour.
- Creator's Favorite: Fujio Akatsuka's favorite character is Chibita, because he found him a fun character to write. He is his second favorite character he created of all time, losing only to Bakabon's Papa.
- Crossdressing Voices: All of the Matsuno siblings and Chibita are hit with this trope in both the Studio Zero series and the 1988 series.
- Fan Nickname: "The Hivemind"/"Hivematsus" for the Matsuno brothers. People coming from Osomatsu-san tend to call the brothers "Minimatsus" instead.
- Fountain of Expies: Is there a wacky adult with a large overbite or a thin mustache in an anime or manga? Does he have a tacky fashion sense? Does he make a silly pose or outright perform the "Sheeeh!" pose? There's a good chance that they're based off of Iyami.
- Market-Based Title: In Spanish speaking countries, the '88 anime was retitled Cosas de Locos (Crazy Things).
- Milestone Celebration: The official 2012 pachinko game was created in celebration of Fujio Akatsuka's 75th birthday. It also came out during the 50th anniversary of the manga's release.
- Missing Episode: More like missing series, as the entire Studio Zero anime adaptation was this for a long time, since the original reels were thought to be lost. However, in the 90s, the films were found in a warehouse.
- No Export for You: Though Kodansha put out a bilingual tankobon of some of the manga volumes, the series in its entirety never made it to the Western hemisphere.
- A noticeable exception being in Spain and other parts of Europe, where the 1988 Osomatsu-kun anime was mixed with Heisei Tensai Bakabon and Rerere no Tensai Bakabon, and released as "Cosas de Locos", where all episodes are complete and dubbed, at least in Castilian Spanish.
- Recycled Script: One of the manga's stories involved Chibita getting out of jail on good behavior, and being forced to use his lockpicking skills to help save a person trapped in a safe. In the original version, it was Osomatsu and Choromatsu who were stuck, but a later version of the story had Totoko trapped inside instead.
- The Beach Episode changed a little between adaptations and revisions. In the original, the sextuplets went to comb for seashells with Chibita while Iyami and a bit character tried to scam them, while in another, the boys and their father went and Chibita joined Iyami in the scam. Totoko subs in for Chibita in the shell combing scene, which takes place much later into the story.
- Quite a few stories from the 1966 series (which itself came from the manga) were recycled into the 1988 show. Some had minor changes, while others had bigger changes.
- The Other Darrin:
- Chibita went through three voice actresses in the 1966 series.
- Yui Shoji took over the role of all six sextuplets for the pachinko game.
- Referenced by...: Believe it or not, Phoenix had a couple of sight gags referencing it: one had Hinaku give birth to quintuplets, prompting 5 of the brothers and Iyami to make a snide comment.
- Talking to Himself:
- In the Studio Zero series, Ichimatsu and Todomatsu were voiced by Haruko Kitahama.
- The 1988 series, two of the Matsuno brothers also voiced supporting characters. Naoko Matsui voiced Totoko and Jyuushimatsu, while Mari Mashiba voiced Hatabou and Karamatsu.
- What Could Have Been: Akatsuka had planned on making dodecuplets (that's TWELVE children!) before the series started.
Trivia / Osomatsu-kun