What anime is this? 
I was watching some random akira videos and I found this easter egg that I never noticed before. I remember seeing an opening of an 80s or older anime about some old police trio or something like that.Could it be possibly based off of this? Manga Mito Kōmon
It's almost certainly an outright reference to the well-known live-action show Mito Komon.
The title character is the historic Tokugawa Mitsukuni, former vice-shogun and retired second daimyo of the Mito Domain. In the guise of Mitsuemon, a retired crêpe merchant from Echigo, he roams the realm with two samurai retainers, fun-loving Sasaki Sukesaburō (Suke-san) and studious Atsumi Kakunoshin (Kaku-san). An episode typically starts with some injustice perpetrated by a corrupt official, wealthy merchant or gangster; the travelers arrive incognito, discover the injustice and quietly investigate it; and the episode concludes with a brawl in which the unarmed, disguised protagonists better a crowd of samurai and gangsters, culminating with the presentation of the inrō that reveals the hero's identity.
I wasn't aware there was an animated version. Mito Komon has been around for decades (1969-2011, over 1200 episodes), like their own version of Doctor Who.
Since it's a well-known part of pop-culture, the show is often referenced or outright parodied, like in Samurai Champloo (Mugen, it'll be our little secret....).
