I Love You Again (1940)
When William Powell wakes up after being hit on the head, he discovers that had previously been in an amnesiatic state which he has now been literally knocked out of. Suddenly remembering that he is a con artist whose last real memory is from 9 years previous, he decides to continue on with the other life, where he is married to Myrna Loy, to pull off bigger swindles. It’s all incredibly silly and a bit convoluted (they don’t even bother trying to explain what happened 9 years ago nor how he started a new life back then) but there’s still the wonderful Powell-Loy chemistry that makes it worthwhile.