Gray Bowser Statues are statues that look a lot like the Koopa King and first appeared in Super Mario Bros. 3. There are Golden Bowser Statues too.
The Gray Bowser Statue will just stand there shooting lasers at Mario should he get too close, and may not be defeated. It also appeared in Super Mario World where it did the same thing.
Lately it has appeared in Mario Kart 64 and Mario Kart: Double Dash!! in the Bowser's Castle courses. In Mario Kart 64, the Bowser Statue would just stand there shooting fire that would not hurt anyone. However in Mario Kart: Double Dash it could move, and it would shoot fire that could hurt anyone.
Other Gray Bowser Statues are not alive and do not move, like the ones in New Super Mario Bros.. These non-living Bowser Statues also appeared in Super Princess Peach, where they decorated the course where the initial fight with Bowser took place. They only appeared in said battle, where they where they could be crushed by Bowser's misused charge attack, resulting in a Crystal for Peach to collect.
They also appeared in Mario Party 2 and Mario Party 8. In both games they appear in mini-games where they need to get hit. They are also non-living. In Mario Party 5, several immobile Gray Bowser Statues appear in the Bowser mini-game, "Dizzy Rotisserie"; if a character doesn't complete this mini-game in time, these Gray Bowser Statue will spring to life a bathe the arena in fire, roasting any nearby characters.
Appearances in Other Media
Gray Bowser Statues, though never named, appeared occasionally in the Super Mario World animated series.
Gray Bowser Statues first appeared in the episode "Send in the Clown", where one attacks Mario by shooting a fireball at him while he is travelling through Neon Castle. Later in the episode, Mario accidently stumbles apon another Gray Bowser Statue, which proceeds to spit a fireball at him; Mario manages to narrowly aviod this fireball, which hits his Koopa Football Player persuers.
In a later episode, entitled "Mama Luigi", two Gray Bowser Statues are shown to act as guards to the entrance of Neon Castle; additionally, a Gray Bowser Statue is also found in the basement of Neon Castle. This Gray Bowser Statue is eventually shut-down by Yoshi, who eats one of it's spat fireballs and blasts the Gray Bowser Statue with flames.