Changkey

Tackle Fire (チャンキー) is a fire enemy from the classic Mega Man series, usually spawned by various other enemies. In Mega Man 2 and Mega Man: Dr. Wily's Revenge an enemy called Hothead creates Tackle Fires. It appears in Fire Man's stage from Mega Man, Mega Man: Dr. Wily's Revenge and the first part of the Wily Tower in Mega Man: The Wily Wars. In Mega Man: Dr. Wily's Revenge, they are invincible and just appear falling into lava. They also appear in Mega Man 10 in Solar Man's stage where four of them fly in parabolic arcs from one turret to another and back.

Changkey R
Changkey R (チャンキーＲ) is a revised version of the Tackle Fire. Though, not much has changed, except that it can now be destroyed. They only appear in the intro stage of Mega Man and Bass.

Changkey Dragon
Changkey Dragon (チャンキードラゴン) is the sub-boss of Magma Man's stage and the first Wily stage in Mega Man 9. It's a skeletal dragon with the body covered by large Changkeys. It rises up and down in a wave-like fashion, while breathing out Changkeys. If they hit the ground, they will roll towards Mega Man.

Its weaknesses are Black Hole Bomb and Concrete Shot. When hit by Black Hole Bomb, the Changkeys will temporarily disappear, weakening the dragon. The Tornado Blow does this effectively as well, but it uses all four shots of it, which is also the weakness of Magma Man himself. For speedrunners, it is fastest to use Concrete Shot. It kills him in five hits, but it's hard to hit the dragon's head with it for it keeps rising up and down. The Hornet Chaser is also a good weapon to use on it, as the bees will almost always hit him as long as the dragon's head is visible.

Changkey in the Battle Network series
Changkeys also appear as viruses in Mega Man Network Transmission. They only show up in the area "Net on Fire." When they shoot up from the lava, they float down and towards their target.

Trivia

 * Changkey was named after the nickname of a Capcom employee.