The Motion-Sensor Bomb is a perfect and famous tool spies used to ambush their foes and will detonate with tremendous power if it senses motion in its range. It is capable to stick on to any surface it lands on. It appears on Super Smash Bros. series as a tricky and sneaky explosive item and trophy. The 1st appearance of this item is written "TOP SECRET" on the trophy and likewise the Cloaking Device trophy in Melee.
The design of the Motion bomb was changed when the game came overseas. The original design was based on Mines from Perfect Dark but, the design was changed to the mines from Goldeneye 007. It has been made "Top Secret" as Nintendo wanted to remove the Rare references from the game as they were selling owned by Rare.
The design of the motion bomb changed in Brawl likely to lower the resemblance to weaponry and remove the design reference. The design was changed once again in Smash Bros. for Wii U/3DS. It now looks a lot more menacing and noticeable.