Michael "Mickey" Patrick is an old friend of Danny Reagan. He was usually the one who got into trouble with Danny to the point that neither Frank Reagan nor Henry Reagan wanted Danny to be around him.
It was in Florida where his real estate deals got him tangled with the Vasquez Family, the biggest crime family in that state.
In the fifth grade, Danny and Mickey developed their own secret language called Ob. It bears similarities to pig latin with ob inserted into words, though the words remain in English spelling arrangement. The structure appears to be ob inserted before vowels or sets of vowels.