"Handy's Sweetheart" is the first of three appearances of Marina the Mermaid.
At one point, Brainy says "East is east, west is west, and never the twain shall smurf." The phrase "Never the twain shall meet" was used by Rudyard Kipling in his 1892 "Barrack-room ballads", meaning two things which are so different as to have no opportunity to unite.