Iggy Koopa

Iggy Koopa is presumably the middle child of the seven Koopalings. He is seen in the Mario cartoons where he is known as Hop Koopa. In the anime however he is known by his actual name.

Super Mario Bros. 3
Iggy is the fourth Koopaling to be fought. He is encountered on an airship in Giant Land. His battle style is similar to Larry's. Once defeated, Iggy ran off, leaving behind the magic wand he used to transform the king of Giant Land.

Super Mario World
Iggy is the first Koopaling to be fought. To defeat him, Mario knocked Iggy into the lava.

Mario & Luigi: Superstar Saga
Iggy somehow returned in Mario & Luigi: Superstar Saga, and appears in Bowser's castle when it is under Bowletta's control. Again, he is the first Koopaling to be fought. Once defeated, he apparently dies and vanishes.

Super Princess Peach
It was revealed that he along with his other siblings were at one point going to appear in this game but were taken out in the final version. They even had a full sprite sheet.

New Super Mario Bros. Wii
Once again, Iggy returned alongside the other Koopalings, kidnapping Peach for Bowser. He is the fifth Koopaling to be fought, in a forest level. He is fought twice. The second time, he is riding a cart being pulled by a Chomp, which Kamek uses a spell to increase his size. Once defeated, Iggy fell off the screen. He survived, though, and was last seen after the credits alongside Bowser Jr., Bowser, and the other Koopalings, before Bowser's castle fell on top of them and crushed them.

Mario Kart 8
Iggy and all of the other Koopalings made their first appearance as playable characters in Mario Kart 8. Iggy and Ludwig were the only two Koopalings to be in the upper medium class.

Super Smash Bros for Wii U and Super Smash Bros for Nintendo 3DS
Iggy Koopa has been confirmed to be an alternate costume for Bowser Jr. in the video games; Super Smash Bros for Wii U and Super Smash Bros. for Nintendo 3DS.

Physical appearance
Iggy wears large black glasses and has green hair. He initially had a blue shell, but in later games, his shell was changed to green.

Trivia

 * Iggy's name is derived from Iggy Pop.