Daphne believable as the object of such idealization?

I believe Niles could be infatuated with her. In my younger days I was irrationally hung up on a few women who, in retrospect, I realize were not exactly "bombshells". But something about the combination of each one's personality, the situation, my state of mind at the time, and whatever physical attractiveness she possessed captivated me.

I think it is one of those crushes you develop over time of knowing someone. That said I think Niles was head over heels at first site. She was also very nice and non threatening, probably something very different for Niles after Maris.

She was really hot on Benny Hill but became too skinny and lost her curves.

Look all around you when out in public. Every single day across the world, people fall head over heels in love and in lust with people who are not perfect paragons of physical beauty, handsomeness or sexiness to most other people's eyes. But to each other they are "it" for them. Thank heavens, too, because if only Sofia Vergara or Megan Fox, or a Hemsworth brother are going to be the only person whose looks get them love and sex, then 95% of the population is in trouble.

People have quirks in what they find appealing and one man's "meh" is another man's "she just does something to me," same goes for women.

I feel as though they deliberately cast a woman who wasn't exceptionally beautiful as Daphne so that women who watch the show could imagine themselves in her place.

It made sense in terms of personality.

In terms of looks they're both attractive if not outstanding, but it's her personality rather than her pretty face that would have attracted Niles. Niles is uptight and status-conscious, over-educated and for all his self-obsession he's out of touch with his own feelings... and Daphne is the opposite. She's an open-hearted, uninhibited free spirit, as well as lower-class, and as such she's the total opposite of both Maris and Niles himself. She is everything that Niles doesn't let himself be.

Well, not really.

A person doesn't have to be flawlessly perfect to have somebody else have a crush on them. Sometimes it's the mannerisms of the person that attracts you as much as their looks. And, as you said, Daphne was hardly unattractive.

I don't think it's implausible at all that somebody like Niles, who had been married to somebody as cold and unavailable as Maris, would find somebody like Daphne attractive.

One of the basic jokes of Frazier was that these two psychiatrists really belonged on a psychiatrist's couch. Each having more issues than Time Magazine, it's not surprising that Niles would develop an obsession with some random woman. And his attraction couldn't just be a mere attraction -- it had to be utter, slavish adoration; an over-the-top emotion that any good psychiatrist would realize probably said more about his relationship with his mother than it did his feelings for Daphne.

I'm with Niles. She's definitely my type. I don't care about boobs. I love legs.