Contrary to popular belief, there is no evidence that Mega Man 5 was banned or failed to release in Vietnam specifically because of Napalm Man's design, the similarities that his stage's design bears to areas within the country (including the Viet Cong's tunnel system used during the Vietnam War), or one of its enemies resembling a tiger species endemic to Vietnam among other similarities. The history of the Vietnamese video game market itself is poorly documented. It is currently believed that all video game imports were virtually banned by the Vietnamese government as a result of Cold War tensions until the implementation of the Đổi Mới reforms started in 1986, which allowed for some second-hand game console imports and rental arcades to pop up. They are thought to have become a more widely available commodity in the country in 1994, two years after Mega Man 5's release, when the United States lifted its 30-year-long trade embargo on Vietnam. It is unknown if there even was a Vietnamese reaction to Napalm Man at the time.

According to a Japanese promotional tape, earlier versions of some of the special weapons function differently than they do in the final game:
• Star Crash was a single attack that homed in on enemies rather than being used as a shield.
• Gravity Hold stopped time instead of defeating all enemies on screen.
• Gyro Attack did not have a limit and it could be used in multiple directions at once.

In Dr. Wily's Castle Stage 1, during the boss fight against Big Pets, there is a rare glitch where the platforms look like they remain stationary, but the game still acts as if they are moving as intended.

Using an M-Tank while Mega Man's health and all his weapons are full will cause all non-boss enemies on the screen to turn into 1-ups.