Mervyn LeRoy's tinsel town connections made for a few interesting cameos in Without Reservations. Look for Jack Benny as an autograph seeker in the train station. Louella Parsons plays a Hollywood radio gossiper. Cary Grant also appears for a dance sequence. Apparently Grant walked by the set one day during filming and LeRoy asked him to come in. Even the director himself makes an on-screen appearance, dining with Claudette Colbert. Dolores Moran and Raymond Burr (an uncredited "Paul Gill") also make uncredited cameo appearances.
The car they buy is an 1933 Isotta Fraschini Tipo 8A Dual Cowl Sports Tourer by Castagna, one of only two known to exist as of 2018. It was sold at auction by Sotheby's in 2017 for $902,000 and has also appeared in Der unsichtbare Agent (1942), Mr. Imperium (1951), Follow the Sun (1951), and--most famously--Giganten (1956).
Claudette Colbert is the fourth and final actress to be billed above John Wayne after he reached star status. He had previously been billed second to Claire Trevor three times, Marlene Dietrich three times, and Joan Crawford once.
Jack Benny: as himself. About 22 or so minutes in, when Christopher "Kit" Madden (Claudette Colbert) is in the train station, Jack approaches her and asks her if she is Christoper Madden and when she says yes, he asks her to autograph the book she is holding (which she wrote) and asks her to make it out to Jack Benny. He first approaches with his back to the camera, so it's impossible to see who he is, but when he speaks, his voice is immediately recognizable. He then self-identifies to verify the viewer's suspicions, but not until she signs the book and moves on does he turn around and face the camera for the final verification.