The Mega Man Robot Masters appeared in "Mega Trouble For Megaland," with Ice Man being referenced in "Nightmare On Mother Brain's Street."
History
These robots, like Mega Man, were created by Dr. Wright, but were stolen and reprogrammed by Dr. Wily.
Five of the Robot Masters were within the corridor of Cuts Man's domain attempting to defeat the N Team (consisting of Kevin Keene, Princess Lana, Duke, and Mega Man). Kevin defeated the majority of them with his Zapper, while Mega Man destroyed one of Bomb Man's bombs.
Cuts Man awaited the team, who found that their firepower was useless. They managed to defeat him by arranging for him to be impaled by his own weapon, due to Duke circling him.
All six Robot Masters were recreated through the use of the Three Sacred Treasures, but were defeated due to the treasures being destroyed by Kid Icarus' newly acquired Fire Arrow.
Some time later, the N Team is trapped in a nightmare world by Mother Brain. Mega Man's worst nightmare is being frozen by Ice Man.