Not to be confused with Stars.
A Starman is an item from the Mario series that makes Mario invincible temporarily. They hide in various blocks scattered across the Mushroom Kingdom. However, they are usually found inside hidden invisible blocks.
In Super Mario Bros., Mario can jump up and hit a block with a starman inside. It then hops out and jumps along the grounds until either Mario gets it or it falls off stage. If the player gets the Starman, the player is able to run through enemies and not take damage. In the Super Smash Bros. series, if a player gets a star, they become temporarily invincible to all attacks and damage afflicting objects, such as bomb items, but the effect doesn't hurt the others players/CPUs, even with contact.
In Mario Kart, the player can find Starmen in item boxes but it is regarded as a more rare item, compared to the Green Shell or Banana Peel. It is slightly easier to get the item if you are closer to last place. Starmen give the player invincibility, making contact with another Player/CPU will knock them with more force than a Red Shell (More stated below.) The character cannot be hit with any other weapon while they are invincible.
If the character touches anyone else on the track with a Starman, that other person will spin out, causing them to stop for a couple seconds. With a Starman, the character can also drive over mud, dirt, or through shallow water easily, making them great for shortcuts.