[Dr. Sivana]

but the series really missed the mark with Tony Randall as Jack Lemmon’s character...

Tony Randall might have moved the character away from Neil Simon's version, which empahasized the OCD/nrurotic side, and not quite so much the neatnik side. The opera buff business was Randall's invention. However, I think Klugman and Randall had great chemistry, clearly irritating each other but caring deeply for each other anyway.

[IrishBrigade]

‘Tony Randall might have moved the character away from Neil Simon’s version, which empahasized the OCD/nrurotic side...’

indeed; you’ve hit the mark precisely...one of the signature moments in the movie was when they had the two girls in apartment, and Oscar goes to fix drinks, expecting a fine evening to ensue (’is everybody happy?’) and upon his return, finds not only Felix but the two previously ebullient girls weeping copiously after Felix tells his tale...I can’t picture the prissy and aloof Randall effectively pulling that off, being incapable of generating the requisite empathy...

but then, I detest television programming in its entirety, so I may be unduly biased...