The Mamas and the Papas have a leading entry in the annals of recording bloopers with Denny Doherty’s premature “I saw her” in the last cycle of “I Saw Her Again Last Night” (1966)—not his mistake but an engineer’s.
Once it’s famous, the happy mistake becomes a calculable hook that can be used again, and Kenny Loggins brings it back in “I’m Alright” (1980).
The original mistake sounds less like a mistake. It works: that’s why it was kept in the first place. The deliberately crafted mistake by Loggins and his crew is actually more disruptive. It makes me feel they piled on one too many excess measures; they seem to be milling around without purpose. It’s the one flaw in a fantastically entertaining track. In short, they made a mistake.
But now I have to think carefully about the true worth of the Loggins mistake. Since it really registers as a mistake, it qualifies as a Mistake Hook, undiluted by Serendipity. In this way it leaves the Mamas and Papas mistake far behind. In fact, my sense of “I’m Alright” revolves entirely around this axial mistake near the two-minute point—I hear everything in the song as Before the Mistake (B.M.) or After the Mistake (A.M.). And I do feel compelled to listen to the song. Therefore the song’s mistake must be a mighty hook, and I am not going against Hooks rules—to praise and not to pan—by pointing it out.
There’s a spirit in this song of throwing in lots of musical goodies. Enthroned in their midst, the Mistake sets them all in pleasing relief.
 According to Bones Howe’s account in The Wrecking Crew.
 That extra measure sounds pretty good when the Mistake is left out—here it is in the live version.