Ann-Margaret, a Swedish-American actress, singer, and dancer starred in what movie with Walter Matthau?
The Sunshine Boys (1975 film):  This would be Matthau's last Neil Simon movie until 1982's "I Ought to Be in Pictures" with Ann-Margret and Dinah Manoff. Ann-Margret: Ann-Margret (born Ann-Margret Olsson; April 28, 1941) is a Swedish-American actress, singer, and dancer.
"I Ought to Be in Pictures"