"DuckTales 2 - Two Players Hack" changelog from version 1.2 to 1.4a:

+ select for 1 player or 2 players game. 1 player game matches original.
+ game slowdowns reduced.
+ improved sprites showing on hardware/with sprite limit enabled.

bugs fixed:
+ fixed bug when player2 can move some objects, when hit them in jump.
+ fixed rare possible game freeze.
+ fixed various graphical bugs.
+ corrected some objects scripts work on player2 when he's on_screen/out_of_screen.
+ fixed bugs with money: player2 now loses own money when he dies, player1 loses only own money.
+ can't more pause/use cake while player2 dying.
+ fixed player2 fall through sand, when player1 stands far from sand.
+ fixed 'restart death bug', when one player dies in sand, and other jumps back from sand.
+ fixed bugs with objects linked with player2, when they goes outside of screen.
+ player2 dialog with npc starts when he's on ground, not player1.
+ fixed 'lock p.2 death bug' when player2 dies, but player1 goes to other floor.
+ some others bugs fixes.

other improvements:
+ in 2pl. mode boss event starts only when two players come to boss arena (except glomgold),
  player2 moves to boss as player1.
+ player2 buttons works on text dialogs.
+ heads sprites in dialogs now have priority vs other sprites.

* darkwing duck pogojump sprite from early version.