Although he doesn't appear onscreen, Keenan Wynn has an uncredited role in this film: he was Aunt Wendy's late husband, Henry, and a painting of him appears above her money safe when she makes withdrawals.
Credited as Teri Hope, look for a very young Teri Garr, prominently featured in most of the major scenes. She's often just to the right of Annette Funicello in the dance and fashion show scenes.
Frequently referred to as an entry in the "Beach Party" film series, with the relatively brief appearances of Harvey Lembeck as Eric Von Zipper and Candy Johnson as Candy supporting that, the fact that major players Annette Funicello, Jody McCrea and Don Rickles are not in their usual roles (Connie, Big Lunk and Big Bang a Martian here instead of Dolores/Dee Dee a nickname, Bonehead and Jack Fanny/Big Drag/Big Drop the man kept changing his "name" with his career in the other movies, respectively) suggests the contrary with much more strength. However similar the characterizations are, they are at least nominally different characters.
Toni Basil, and Teri Garr - who appear in the clothing/modeling scene - had a history of working as dancers together. They were also featured in ShInDiG! - which Ms. Basil also served as choreographer on.
Toni Basil:
During the 'fashion show' at Dorothy Lamour's store, watch for the last model who comes out - it's young choreographer, and eventual singer of "Mickey", Toni Basil.