Monstar

Monstar is a ghost-like monster from Paper Mario and is a mini-boss who attacks those who enter Starborn Valley. When Mario and his friends first encounter it, Monstar appears tough to defeat, and Monstar is invulnerable to Star Spirit attacks and the Shooting Star item. However, Monstar is nothing more than some Star Kids trying to protect their home. When Monstar attacks, it makes a light show with special effects. However, the attack deals only 1 damage point. After attacking, in a shaky voice, it asks Mario if he is scared yet.

Monstar also appears in the 27th issue of Super Mario-Kun. It terrifies and attacks Mario, Goombario, and Kooper, but when Mario defeats it, many Star Kids reveal themselves and escape, surprising Mario and his group.

Trivia

 * Monstar name is a pun on monster and a portmanteau of "monster" and "star".
 * Monstar also happens to be the name of one of Starfy's transformations in the 2009 DS game The Legendary Starfy.