Unshelled Koopa
A Beach Koopa is a Koopa Troopa that has lost its shell and wears nothing more than an undershirt (and/or in some cases, boxer shorts). In Super Mario World, the Blue Beach Koopas will kick shells they come into contact with. The Yellow variety, on the other hand, will go into the shell. Instead of emerging as a normal Koopa Troopa, however, the shell will begin to spin wildly and flash different colors. Beach Koopas were also found in Super Mario World 2: Yoshi's Island and Yoshi's Island DS, although here, they walked upright when evicted from their shells, instead of on all-fours as in Super Mario World. This version of Beach Koopas make a small appearance in Paper Mario, as the inhabitants of Koopa Village who have had their shells stolen by Fuzzies.
In Super Mario 64 and Super Mario 64 DS, Mario or others could jump on a Koopa Troopa to knock its shell away, transforming the turtle into a Beach Koopa. If attacked again, the Beach Koopa would be destroyed and a Blue Coin would pop out. If not defeated, the Beach Koopa will frantically attempt to dive back into its shell. Mario can ride on this green shell.
Beach Koopas reappear in Super Princess Peach.
Even Bowser has a "Beach Koopa form" (wearing spotted boxer shorts) when separated from his shell, as shown in the PC version of Mario is Missing!.
Appearances in Other Media
In the Super Mario World episode "Fire Sale", the silent, Koopa Troopa henchmen of Kootie Pie Koopa is continually knocked out of his shell, becoming a Beach Koopa, in the episode, usually during one of Kootie Pie's violent temper-tantrums.
