Chicken Walker

"Oooooh! It's got chicken legs!"

—GIR, Invader Zim

Most tanks have tracks, some tanks have legs, while others have many, many legs. These tanks on the other hand, have chicken legs, or as they're officially known reverse-joint or digitigrade legs.

Most of the time a Chicken Walker is a Humongous Mecha or Mini-Mecha but occasionally backwards bending legs pop up on cabins or other objects as well. While there may be some benefits to a leg shaped like this, it doesn't overcome the fact that these are inherently funny (though you'll find most, if not all military-themed series will be taking them very seriously).

Also note that chickens don't actually have "backwards knees", because the apparent "knee" is actually their ankle and heel joint, while their actual knee is much closer to the body (and practically invisible under their coat of feathers).

For other awesome tanks check out Hover Tank, Drill Tank, and the Military Mashup Machine.

Examples of Chicken Walker include:

Anime and Manga

In Super Dimension Fortress Macross, Super Dimension Century Orguss and Super Dimension Cavalry Southern Cross, the mech knees bend forward in full-humanoid battroid mode but backward in jet-with-legs GERWALK mode.
- Macross' Zentradi combat pods like Regult and Glaug also fit this trope.
- Earth mechs with Armo-Diver mode and the non-humanoid Invid mecha from Genesis Climber Mospeada.
- Most of the above also appear in Robotech, of course.
Although rare in Gundam, a few MS have reverse-joint legs when transformed, notably the Gaza-C, its successors and Destroy Gundam.
Xabungle has quite a few.
20th Century Boys: the robot design the engineer whose daughter the Friend cult kidnapped ended up this way, instead of the blatant Tetsujin 28 ripoff they originally wanted.

Film

Star Wars has the AT-ST's and their various derivatives/precursors. In fact, they are often called "Chicken Walkers" by fans.
RoboCop has ED-209. Heavily armed, very strong and intimidating, can't even walk down a flight of stairs...

Live Action TV

From Kamen Rider Faiz, the Side Basher in Battle Mode.
The Blue Midget from Red Dwarf was retconned into one of these, originally being a tank-like vehicle.
Falling Skies: the "meks" of the aliens walk this way, but are weirdly designed.
- Several characters discuss the possibility that the meks were specifically designed to intimidate humans, as the aliens themselves are six-legged. On the other hand, it could be a purely technical decision. It's not practical to build a large robot with more than 2 legs (4 max).

Mythology and Folklore

Baba Yaga's house moves around on actual giant chicken legs.

Tabletop RPG

Warhammer 40,000 has variations of the Sentinel (light all-terrain reconnaissance vehicle / very modest weapon platform) and Warhound Titan (bigger than a superheavy tank, but gets to be a reconnaissance vehicle in Titan Legions) for the Imperium, the Eldar War Walker (like a Sentinel, but better made), etc. While Titan are anime grade stuff, small walkers are treated more realistically as slow Glass Cannons - their only advantage being ability to ignore pretty much any rough terrain including rock slides and tank traps. Otherwise, common light tracked or wheeled vehicles have much greater speed with comparable armor and weapons, even in the same size category (Tauros, Tauros Venator), and if size and being air-droppable don't matter, amphibiousness and better armor (Chimera APC, its Salamander Scout and Salamander Command variants).
- The Tau's battlesuits are closer in appearance to actual chicken legs than this trope, what with forward bending knees, high ankles, and several widely spaced, broad toes.
Roughly half the bipedal BattleMechs are like this, including fan favorites like the Timber Wolf, Mad Dog, Bushwhacker, and Marauder, the rest using standard humanoid leg structure. Acknowledged by supplemental material by noting that chicken-walkers may traverse rougher terrain but are typically less speedy than man-walkers.

Video Games

World of Warcraft has some actual giant mechanical chickens that function as mounts.
- More like mechanical ostriches or emus.
Command & Conquer the GDI uses these as artillery.
Some of the early Metal Gear models followed this design, although more advanced ones went for forward-knee designs. The birdlike look is actually lampshaded in the manual, which claims that the small, unmanned Metal Gear Gustavs are nicknamed "Ostriches" by troops because of the way they walk.
The Goliath unit in StarCraft.
Basically the whole idea of Future Cop: LAPD. Well, that and Flying Cars.
The Raptor from the second G-Police game. It had the ability to jump and glide (compared to most of the vehicles being planes, with one example of an armoured car).
You can find many of this in Armored Core series. Befitting of a bird-inspired design, they're better in the air.
The first boss from Super Meat Boy called Lil' Slugger is one armed with saws and a chainsaw.
Biomechanoids from Serious Sam series are like that. Coincidentially, the biological parts of these walkers are bird tissues.
- There is a Chicken Walker enemy in Serious Sam II, too which is called Torso Mech - The Nervous Chicken.
Mechwarrior, being based off BattleTech, gets in on this as well with quite a few reverse-joint 'Mechs. The games give some of them a marked hopping-bobbing gait, which can be a bit tough on targeting at times. Chicken walkers in the games typically move faster, but aren't as good at scaling hills or mountains as man-walkers.
In one level of Futurama: The Game, you get to ride in a literal Chicken Rider.
A literal one in Donkey Kong Country Returns, which serves as the boss of World 7. And yes, it's piloted by a chicken.
In Chrome Hounds, you can build your very own, officially known as reverse-joint chassis. The leg form gives enhanced recoil consumption, making them good for light artillery and sniper mechs.
The Flapper species in the economics edutainment classic MULE. No surprise, since they are human-sized birds.
The Star, Panzerstar and Sturmvogel enemies/boss from Einhander. Interestingly enough, their names mean "Starling", "Armored Starling" and "Thunderbird" in German, quite meaningful when compared to their bird-like legs.
In Mass Effect, a majority of the bipedal aliens you encounter have this leg structure, including turians, salarians, krogan, and quarians. Geth also fit the mecha version of the trope (and in some cases, the Humongous Mecha version), as their bipedal forms are based the physiology of the quarians that created them.

Web Comics

Problem Sleuth's candy mecha is a sentient example. In fact, even after the head is detached so that it can fly off to fight the villain, the legs still are used for various purposes.

Western Animation

Chaotic featured the Vile Driver card in some episodes.
Kim Possible had giant robotic flamingos.
Invader Zim once received a MegaDoomer stealth mech due to a ~~pathetic attempt at sabotage~~ shipping error. GIR was fascinated by its legs (see page quote).
On Jimmy Two-Shoes, this is one of Heloise's many machines.