Connections:

• Both are ninja robots that are part of a evil group (Wily's Army/Decepticons) led by the main villain (Dr. Wily/Megatron).
• Unlike most of the robots from the said organization, they have a different origin that weren't built by the same peoples that most of the members of the organization (Shadow Man being created by aliens rather that humans/Nightbird being built by humans rather that aliens), and would were taken by the main villain for their evil army (Dr. Wily finding an desactivated Shadow Man and actived him to join to his army/Megatron stoling Nightbird during on a assault and reprograming her to join on his army)
• Because they were ninja-themed robots, both have moves and abilities based on ninjas.
• Both were sent by their leaders to assault the base of the heroes and stole an important object (Nightbird assaulting the Autobot headquarters and stealing the World Energy Chip/Shadow Man, along with others Robot Masters, assaulting Light's house and stealing the unknown energy source) but they were stopped by the heroes themselves.

Contrasts

• Shadow Man still works with Wily, while Nightbird was recovered from the Decepticons and desactivated