Continuity mistake: During the scene where Brodie talks to Jay and Silent Bob about Bluntman and Cronic, he shows them a copy of Wizard magazine with a related article. On the right page is a picture of Holden and Banky. They then take this magazine and eventually show Holden McNeil the same article. The right hand pictures are different from how they were before.
Continuity mistake: In the comic store, "Brodie's Secret Stash," if you press "pause" right when Brodie reaches for the Bluntman and Chronic comic book to show Jay and Silent Bob, you will see that he is right across a comic entitled "Cable." To the right of that is another comic, "Captain America," and if you can recognize it, to the right of the "Captain America" comic is a "Captain Marvel" comic. If you look behind Jay, you can see the same exact thing.
Answer: Apparently it was a song that was improvised by Jason Lee and Jason Mewes. Stated on the commentary.