Porcupo

Porcupo are black or purple hedgehog-like creatures found uncommonly in the Mario series.

Super Mario Bros. 2
In their first appearance in Super Mario Bros. 2, they pace back and forth and are usually in groups of around two or more. To defeat a Porcupo, a player must throw objects at the Porcupo, such as other enemies.

Super Mario Advance 4: Super Mario Bros. 3
Porcupos were also in Super Mario Advance 4: Super Mario Bros. 3, but only in the Japanese E-World Level, Koopahari Desert.

Super Mario All-Stars - 25th Anniversary Edition
Porcupos reappear again in the Super Mario Bros. 2 remake of Super Mario All-Stars - 25th Anniversary Edition, behaving exactly the same as in the original.

The Super Mario Bros. Super Show!
Porcupo made only one small appearance in The Super Mario Bros. Super Show!, with one appearing in the episode "On Her Majesty's Sewer Service" as the pet of Koopfinger. When Mario and Luigi invaded Koopfinger's hideout though, this Porcupo simply hopped off Koopfinger's lap and ran away instead of trying to fight Mario and Luigi with Mouser, Tryclyde, Vampa White and a Koopa Troopa.

Trivia

 * Although Porcupo never appeared in the series again (outside of the aforementioned E-World level), Harry Hedgehogs from Super Mario World 2: Yoshi's Island and Spinies from Mario Kart 64 have both been Hedgehog-like enemies resembling Porcupo.
 * In Super Mario All-Stars, there were only purple Porcupo.