From what I've heard about Guy Ritchie's "Snatch", one of the highlights is seeing Brad Pitt's Mickey speaking in that indecipherable dialect which probably left the other characters and viewers alike scratching their heads about what he'd just said.
I've realized over time about how varied the dialects are in the United Kingdom and the United States, and also having lived in Japan, I also know that there is also quite a number of dialects there, too. When I was living in Gunma Prefecture up in the Japanese Alps, I heard plenty of the local thick dialect, and the Tohoku region up north apparently has a number of local dialects that only the insiders can comprehend, let alone speak in. One variety show which I used to watch had a regular segment where the camera crew went to the deeper areas of certain far-flung prefectures where they had the folks converse in their thick-as-molasses dialects after which the tarento featured on the show that week had to somehow interpret what they said.
As some of you might already know, my family basically comes from the Kansai area of Japan which includes Metropolitan Osaka and Wakayama Prefecture. Folks there are also known for their distinctive way of speaking and being very boisterous about it. Quite a while ago, I discovered this song by Miss Hanako（ミス花子）, "Kawachi no Ossan no Uta" (The Song of the Old Man From Kawachi). First off, just to let you know off the top, Miss Hanako is no lady. Miss Hanako is actually male singer-songwriter Kazutoshi Kagitani（鍵谷和利）who originally hailed from Nara Prefecture but mostly works in Osaka.
Now, as for that dialect...yep, Miss Hanako really lets it rip with the local lingo which I believe is Osakan since the speed and vocabulary remind me of what was being bantered all around me when I visited my relatives years ago (mind you, when he sings the title, it all comes out smooth as glass). Basically, the old man in the song is a true salt-of-the-earth friendly guy who everyone in the neighbourhood of Kawachi, Osaka knows. The melody by Miss Hanako has got that funky folk-rock vibe which probably made it ideal for covering by future singers and bands.
Ironically, though, the local flavour of "Kawachi no Ossan no Uta" didn't please the higher-ups at Teichiku Records who basically labeled the song as "crude". So it was Columbia Records that came to the rescue and released it after which the song hit No. 5 on Oricon after coming out as Miss Hanako's debut single in August 1976, selling around 800,000 records.
Later that year, an entire movie was built around "Kawachi no Ossan no Uta" with actor Takuzo Kawatani（川谷拓三）playing the titular grizzled old guy as a truck driver who'll even take on the Yakuza.
And here is Miss Hanako in the flesh performing the song in 2016.