25m

25m is the first level in Donkey Kong and the first ever level in the history of Mario and Donkey Kong games.

Appearence
25m is a large stage where Mario must move toward the top using ladders in order to reach Paulina. The stage itself has the same color scheme as the later level 75m being mostly red and green.

Hazards
The hazards that appears in this level include:
 * Barrels: The main enemies in this level. Donkey Kong throws an infinate amout of barrels attempting to stop Jumpman.  They can be difficult to avoid since they tend to go down the ladders without warning. Donkey Kong always starts off with a Blue Barrel that spawns a Fireball. That barrel is most likely contains gas. The barrels, however, can be taken out with hammers.
 * Fireballs: These enemies appear everytime Donkey Kong throws a Blue Barrel into the oil can at the very bottom of the stage. The fireballs in this levels pose very little threat since they appear at the very bottom where Jumpman is nearly at the top already. They can also be taken down with hammers and they could also climb the ladders.
 * Donkey Kong: The main antagonist. Just running into him instanly defeats Mario. This is rather rare since one will already climb the ladder to reach Paulina.

Trivia

 * The scene where Donkey Kong jumps on the stage making it slanted and throwing barrels has become very popular in other video games, television shows, and even movies.
 * Few examples include the Yeti against Sam in the Cartoon Network television show Total Drama: Revenge of the Island and Megamind's partner Minion training against Titan in the movie Megamind.