Black Shy Guy
From the Super Mario Wiki
Black Shy Guys are Shy Guys which wear black robes and white shoes.
They first appeared in Yoshi's Story as a type of Propeller Shy Guy. Black Shy Guys seem to have a horrible taste to Yoshis, because when eaten, Yoshis look disgusted and lose three petals from their Smile Meter. Black and White Yoshis seem to be able to tolerate these and gain two petals. These Shy Guys first appeared on Stage 3-3, Poochy and Nippy. On this level, the Black Shy Guys hovered around in the air and dropped bombs on top of any Yoshi passing by. Surprisingly, this could be used to the Yoshis' advantage, tricking the Black Shy Guys into breaking blocks instead of harming Yoshis. Black Shy Guys also appeared in Page 6, hovering about in the air holding Anvils, which they would drop on any unsuspecting Yoshi that passed underneath them.
Black Shy Guys appear in Paper Mario as Anti Guys, despite their masks being a dark shade of gray. This species would have appeared in battle in Paper Mario: The Thousand-Year Door if Shy Guys had not been cut from the game's roster.
A Black Shy Guy also appears in Mario Superstar Baseball as a playable character and reappears in Mario Super Sluggers as a coloration of Shy Guy. In Mario Super Sluggers, however, it is renamed Gray Shy Guy.