Mark raises a very interesting point about the credits, and one which suggests that they might not always be accurate. "Old Ladies Seldom Powershift" is credited to both Jan and Dean, but it is an instrumental. Which bit of it did Dean write then?
Several possibilities come to mind. Dean came up with the title, it made Jan laugh, he gave Dean a credit. Alternatively, Dean's contributions were real but scattered across the songs, and Jan credited him with the instrumental because he deserved some songwriting royalties from the album, so why not credit him with this one.
I raise the second possibility because Dean has suggested several places that the atmosphere was collegial, with people throwing in ideas and contributing in an ad hoc way. This might suggest that th credits were not always shared in a musically accurate way, but on a much looser basis.
Of course its always possible that Dean came up with the melody to the instrumental and Jan expanded upon it and it WAS a completely musically accurate credit. Maybe.
In the case of "Old Ladies Seldom Power Shift," Dean came up with the title and Jan gave him a songwriting credit for it.
But it's much deeper than that. You have to understand that "Old Ladies Seldom Power Shift" was originally titled "Mr. Chan," a song written by Jan Berry.
It was later re-titled "Bucket Seats" and released on the "Rally-Packs" single on Imperial with "Move Out, Little Mustang" (also co-written by Jan). But since Jan purposely withheld his songwriting credits in an effort to bypass his obligations to Screen Gems and place the publishing for these songs with Trousdale Music, Jan gave Don Altfeld the credit for "Bucket Seats." Jan arranged and produced both sides, but again withheld his production credit in order to place the production with Dunhill.
This was all part of Jan's scheme to branch out and make additional money through other publishers and other production companies. But Screen Gems found out and busted Jan for it, and the "Rally-Packs" release mentioned above was one of the reasons Jan and Lou Adler were sued by Screen Gems in 1964.
When it came time to flesh out
The Little Old Lady from Pasadena LP in late '64, "Mr. Chan," aka "Bucket Seats," still counted against Jan's Screen Gems quota, so the title was changed to "Old Ladies Seldom Power Shift" . . . and Jan gave Dean credit for the title. Thus, Dean got a songwriting credit for it.
The details are in my book. There was much more to the lawsuit.