Frankie's "buffoonery" at the 1st Communion party was brought on entirely by drunkeness. When he showed up to see Mike, he was insulted that he had to wait in line, just like every body else. While waitng, he drank himself into a stupor, and was awaken by Cicci when Fredo showed up.
Now, let's try to be accurate. There is nothing in any scene to indicate that he drank himself into a stupor. He was complaining about waiting in line. Even Connie told her mother that she didn't want to wait in line. Nothing surprising about such a complaint. As some have already posted and as I posted, Frankie was a NY wiseguy who was used to the old school ways, used to Italian food, used to Italian music, ansd wanting to give his enemies as good as he expected they'd give him. There's nothing unexpected about his behavior or words.
