I found out you're a dude - Christakis

 This one is sure worth watching.  I sure wish I spoke Greek and had a deep knowledge of Greek cinema; with those skills I would be able to definitively state what the heck is going on in this video.  Here is my take -- this seems to take place in some place of detention (definitely not a full fledged "Jailhouse Rock" penitentiary).  A fellow is escorted in and Christakis immediately begins singing (and having high spirited conversations) about Mangas; there are also some awesome dance moves!

According to Gail Holst, The Mangas were men who formed a sub-culture on the fringe of society... The nearest equivalents in English are probably 'spivs', 'wide boys' or 'hep-cats'. *    Maybe in light of the title, 'Mangas' and 'dude' are interchangeable.**  

If the comment section, as translated by Mme Google is to be believed, this is from the 1968 film O tycherakias (The Lucky Guy), with the song by Kostas Skarvelis.

As I've said before, many of these musicians lived extrodanary lives.  If the notes below another Kristakis video (again, as translated by Google). are to believed, Christakis...

Left an era during the years of the dictatorship for his interpretive temperament and his figures on the dance floor. Greece's "Johnny Halliday" was summoned. Christos Syrpos, as his full name was, was born in 1924 in Istanbul. He came to Greece with his family and settled in Drama, where he initially worked as a plumber. He got into singing with the prompting and help of the great rebbe Kostas Kaplanis. In the period 1950 - 1967 he sang second voice and played guitar and baglamadaki next to the biggest names in folk music (Poly Panou, Iota Lydia etc.), both in Discography and on stage. From 1967 he started a solo career with great success. He was the first name in the beach shops ("Deilina" etc.) and entertained their patrons until morning. He had a habit of singing lying on his back on the dance floor, piles of broken dishes covering him.

He paid dearly and unjustly for the coincidence of his mesuranization with the black period of the junta of the Colonels. The post-political rage against the fascist dictatorship and its collaborators cast him into excommunication and obscurity. At his last concert in Lycabettus, in '82, there were only 15 spectators. He died penniless and was buried in Drama.

His contribution to Folk Music began to be recognized 10 years after his death.***

*From Road To Rebetika, 1975, pg. 14.  She also mentions that many of the Mangas were in the underworld.

**Upon further working of the word μαγκας (Dude in the title) Google brings out the following possible synonyms; tough guy, crafty, bloke, smart, guttersnip, hoodlum and hooligan.

*** ΧΡΗΣΤΑΚΗΣ - Είναι το κρύο τσουχτερό.  It's the bitter cold. https://youtu.be/qKcgh0l7Wf0