"Samantha And Darrin In Mexico City" (#3903) aired at 8:30 p.m. (EDT) on ABC as the 170th episode of Bewitched (http://www.bewitched.net/). In it, Darrin, after offending Endora, disappears whenever he speaks Spanish.

This was the last new episode of Bewitched (http://www.bewitched.net/) to be telecast in its fifth season, as well as the final on-screen appearance of Dick York as Darrin Stephens.

It was definately the last Dick York episode aired bu tI've always doubted whether it was the last one made as he still looks very well in that episode whereas the earlier one where he is turned into a mule by Maurice shows him looking very thin and ill indeed. Also in "Mexico City" episode no mention is made of Samantha being pregnant which was announced in an earlier episode which makes me think the producers held back this episode from possibly the middle of that season to make it look like Dick York was still appearing in his full role. What do other fans think?

It is true that Episode #170 Sam and Darrin in Mexico City was not York's last episode filmed. The last episode he filmed was Daddy Does his thing #167. It was on that show that York had a seizure on the set and had to be rushed to the hospital. It was reported that producer Bill Asher paid him a visit and York decided to quit the series. Episode 170 was filmed early on in the fifth season and as was said before that episode was held to make the viewing audience that York had been around for the entire 5th season. The 5th season he missed a total of 8 episodes.
As for his appearance, I think for much of the 5th season he looks thinner and tired. The chronic pain and addiction to painkillers are probably the reason for his looking somewhat more rundown in his last season. Hope this info helps.