These are real veterans in the trying-to-stop-Mario-from-reaching-Bowser business and have really developed through the years. When Mario stomps on them he can use their shells to kick on other enemies (Or surf around on their shells as in SM64). In SMB1 they died when Mario stomped on them but now they are harder and has learned the tricks to get out and then quickly crawl inside their shells again. The first time Mario faced these guys was in Mario Bros but then they were named Shell Creepers instead. These guys exists in loads of different variations and colors.
Shell Creepers
The ancestors of all the Koopa Troopas that appeared in Mario Bros.
Green Koopa Troopas
The normal Koopa. When Yoshi eats one of these he can spit out his shell.
Giant Green Koopa
Troopas
These Gigantic Koopa lives in the Giant Land in SMB 3 and are like everything
else in this land extremely big.
Red Koopa Troopas
The red ones are a little bit smarter - they always turns around when they come to an edge, and they also gives Yoshi the ability to spit fire if he eats them.
Giant Red Koopa
Troopas
These Gigantic Koopa lives in the Giant Land in SMB 3 and can like their
smaller versions also turn when they come to an edge.
Blue Koopa
Troopas
The blue Koopa Troopas is a bit faster than the other Koopa Troopas and gives Yoshi the ability to fly for a moments time. When they have been pushed out of their shells they can jump over things that Mario kicks at them and if they find a empty shell they will try to kick it back after Mario!
Yellow Koopa
Troopas
The yellow ones gives yoshi the ability to cause small earthquakes when he jumps (if Yoshi eats them). If you jump on one of these and they makes the way back to their shells they will go cray and become an extremely dangerous flashing homing shell!
Flying Koopa
Troopas
These koopas has developed wings and flies or jumps around instead of walking.
Gigantic Flying Koopa
Troopas
These Gigantic Koopas has also developed small wings and jumps around instead of walking.
Super Koopa
Troopas
These Koopa Troopas has got a cap which helps them to fly around the courses. If Mario stomps on the Yellow Super Koopa Troopa they will just die but if it´s a red one Mario will get a feather from him.
These are more "advanced" Koopa Troopas that have learned to walk upright and to use tools in their struggle against Mario.
Hammer
Brother
Original and the best! these guys throws deadly hammers after Mario and are in pairs quite deadly.
Flying hammer Brother
These rather fat Hammer Brother rides on a platform with wings and throws hammers all around him hoping that eventually some of them will hit Mario.
Boomerang
Brothers
These are equipped with boomerangs. They live in the Deserts.
Fire Brothers
These hot-tempered creatures lives in the desert and are very rare, but if Mario do face one these he better be at least Super Mario to have a fair chance of beating them.
Sledge Brothers
When these fat hammer brothers jumps and then lands again they cause small earthquakes that stunnes Mario for a short period of time making him an easy pray for the Sledge brothers big sledges.
Sumo Brothers
The Sumo Brothers appeared in Super Mario World. When they stomp on the ground, there a small.
Magi-Koopas
These strange Koopas gained powerful magical capabilities from Bowser. They guard Lemmy Koopas castle in Vanilla Dome from unwelcome intruders. With their magic wands they can cast powerful spells that except for harming Mario also has the ability to turn blocks into enemies! They also got the handy ability to be able to teleport around the rooms as they wish. Although that they have some impressive Offensive attacks they certainly lacks in defence. A single jump on their head is enough to bring em down!
Lakitu is flying around in his smiling cloud high up in the skies looking for "you know who" to bombard with deadly spinies (or spiny eggs in SMB 3). In SMW tried fishing but its no wonder that Mario doesn´t bite when he uses a spiny as bate! On some courses he hides in pipes and throws spiny at Mario from there and when Mario and his friends enemies battle out in a game of Mario Kart he is the one who starts the races and helps the drivers if they drive down I the ocean or something! In SM64 one Lakitu floats around after Mario and films his whole adventure for a Tv-show or something....
Koopa The Quick
This Koopa challenges Mario to run against him 2 times through the games. The first time to race him to the top of the mountain in the Bob-Omb battlefield where Mario battled out with the King of the Bob-Ombs earlier. When Mario meets him the next time in Tiny-Huge Island he has gotten himself some new sprinting shoes and thinks that he can beat Mario.