Someone on GameFAQs just said that " Ninetales (which really sucks; I would've liked to have a Droughttales that had Magic Coat), Golduck, Primeape, Machamp, Gengar, Tyrogue, Blaziken, and many more" can no longer get Magic Coat. It seems s/he is basing this off of Serebii's Pokedex, which is apparently incorrect (Bulbapedia and Veekun do not list these Pokemon as learning it).
I just grabbed a Blaziken and took it to the HG/SS tutors and no one offered to teach her Magic Coat. It would seem that Smogon also has several Pokemon incorrectly listed as learning this in Gen 4.
(copied from the objective changes thread because apparently I can't search for the correct thread to post in)
The gen 1 description of Rock Throw says its accuracy is 90%, but its accuracy should be 65% according to every reliable source I could find. I've personally confirmed an accuracy of ~70% with my copy of Yellow version.
Low Kick should simply have 50 BP, 90% acc, and a 30% flinch rate in gen 1, and 50 BP, 100% acc, and a 30% flinch rate in gen 2. The damage calculation being based on the opponent's weight was only a thing from gen 3 onwards.
I guess nobody's noticed it before, but Tri Attack, at least in Gen 2, can thaw out a frozen target. I don't know the percentage chance of it occuring, though. I had it happen in Stadium 2, so those who spam a frozen Pokemon with Tri Attack, be careful!