Returning actors did not age well
Judge Reinhold (age 66) looked terrible - and that was before his days of torture. He did his best to hide his excess weight but he wasn't looking good.
John Ashton looks his age (age 75) but he wasn't believable because he obviously should have retired decades earlier to address all the health issues he described in his first scene. And he made clear that he lacked interest in the job. If he just wanted time away from his wife, there are plenty of less stressful things he could be doing.
Paul Reiser looked fine (age 67) but I wouldn't have even recognized him. Both his appearance and his line delivery were nothing like before.
Bronson Pinchot (age 64) wasn't looking too good for his age but I enjoyed his delightfully weird speech issues although I continue to wonder what his native language was supposed to be.
Eddie Murphy (age 62) has aged well. I guess it helps when you're worth $200M and can afford to take it easy and enjoy a first-class lifestyle.
PS: I've listed their age as their real age minus 1 to account for what it was when filming.