Super Tails

Super Tails (スーパーテイルス) is the Super State of Miles "Tails" Prower, obtained by using the power of the seven Super Emeralds. This originally occurred in Sonic the Hedgehog 3 & Knuckles and has not appeared since then until the 2013 re-release of the original Sonic the Hedgehog as a hidden feature. Super Tails appears in the final battle of Sonic Heroes, though this time by having power shared from Super Sonic.

Appearance
Unlike most other super transformations, Tails himself does not display any physical changes. Instead his fur pulses in a golden yellow color and he becomes surrounded by four super transformed Flickies. In Sonic Heroes he is simply regular Tais but with a glowing yellow energy shield.

Powers and abilities
Following the traditional super transformation, Super Tails is invincible, and as shown so far, to any attack, since he hasn't encountered any foe that can actually damage him. He has increased strength and can therefore break through obstacles by simply walking into them, and also has increased speed. He can also summon super transformed Flickies which will home into any nearby target, boss or enemy, and deal one hit worth of damage.

Like most other super transformations, Super Tails requires Rings to maintain this transformation and will change back to his normal form once he runs out of rings.

Sonic the Hedgehog 3 & Knuckles
Originally seen in the complete lock-on of Sonic the Hedgehog 3 & Knuckles, the Super Tails transformation is enabled only after passing all 14 Special Stages and collecting Super Emeralds as Tails only. The player is then able to activate the Tails' Super Form by normally collecting 50 rings and press jump button twice. After this, Tails glows golden yellow as four golden Flickies appear to fly around him. During the transformation, Tails' fur constantly glows a golden light. Like other transformations, it costs one ring per second while the transformation is being used. When the ring count is zero or when the Act Boss is defeated, the transformation runs out as Tails turns back to his regular form and his Flickies fly away.

Sonic Heroes
Super Tails appears as the Fly Type member of Team Super Sonic. He takes on the form thanks to Super Sonic sharing chaos energy with him and Knuckles so that they can fight Metal Overlord.

Sonic the Hedgehog (1991)
In the 2013 re-release of the original Sonic the Hedgehog, Tails is not only an unlockable game mode, but all seven Chaos Emeralds (and a new final Special Stage) can be enabled as a bonus with the enhanced level select code. In this appearance, Tails can indeed transform into Super Tails with only the Chaos Emeralds, and it almost identical to the actual Super Emerald-powered Super Tails except for the lack of Flickies. However, this is considered a completely non-canon extra exclusive to this release since Sonic and Dr. Eggman have not officially met Tails until after the events of the game, and the seventh Chaos Emerald had only recently been discovered on West Side Island according to the full storyline of Sonic the Hedgehog 2.

Sonic the Hedgehog 2
In the 2013 re-release of Sonic the Hedgehog 2, Super Tails is only accessible via Debug Mode by placing the S Monitor and then breaking it. His appearance and abilities are identical to that in the original Sonic the Hedgehog.

Unofficial ways to transform
Even before Sonic the Hedgehog 3 & Knuckles, there are ways to initiate the transformation in previous games, which are never meant to do in games. This can be achieved using cheat codes or the game's Debug Mode. These transformations don't feature Flickies on Super Tails' side at all.

Sonic the Hedgehog 2
A simplistic form of Super Tails can be achieved in the console versions of Sonic the Hedgehog 2 with use of the debug mode. Whilst Sonic is in his Super Form, placing a monitor and breaking it will cause Tails to be surrounded by Invincibility stars (yellow while Sonic is Super, blue otherwise), have increased speed (on par, if not faster, than Sonic) and invincibility. This happens due to the fact that the default monitor in Sonic the Hedgehog 2—the 2-player Vs. Mode "Teleporter" monitor—not only switches players' positions, but players' statuses as well. (Shield, Speed-Up, Invincibility, etc.) Another peculiarity with "Super" Tails is that even if Sonic loses all his rings or Tails has to catch up to Sonic for some reason, Tails continues to be invincible and super fast.

This can also be done without the debug mode. First, the player must collect all of the Chaos Emeralds in 1-Player Mode. After doing this, the player will have to find a way to lose their lives or complete the game, and enter the 'Options' menu. After that, if the player highlights 'VS Mode items' and presses the START button, then they will enter the 2P level select with all of the collected Emeralds. If Sonic collects fifty rings and jumps, he will transform into Super Sonic, but with his sprite jumbled (the game's attempt to match regular Sonic's sprite size since he can't transform in 2P normally). If Super Sonic smashes a teleport box whilst in transformation, the Super Form will transfer to Tails. Sonic still appears Super (but isn't), and due to the game's engine he won't be able to get invincibility or gain his Super Form abilities again until he loses all of his rings (and, to get Super, collects fifty rings again). The reason Super Sonic is attainable in the VS mode is because the number of Chaos Emeralds collected is carried when accessing through the Options menu.

It should be noted that while Sonic will appear to still be in his Super Form and will still lose rings, he won't have speed or invincibility and therefore will lose rings when damaged. Oddly enough, he does retain his high-jumping ability.

Sonic the Hedgehog 3
Tails can also enter the transformation in Sonic the Hedgehog 3 (without Knuckles) via Debug Mode. If Tails smashes the special monitor with S on it, he gains invincibility, the ability to crush non-Knuckles Spin Dash-only breakaway objects by walking through them (like Super Sonic). As well as a sparkle affect when hitting beyond his normal top speed, but gains no glow, no palette changes, no enhanced jumping ability and no super speed.

At a guess, Tails' Super State wasn't finished (or possibly even started) by the time Sonic 3 was released. His sprite will also be jumbled in the game's attempt to match Super Sonic's sprite size (since Tails can't get Super normally) unless you press the Debug Mode button after hitting the S-Monitor, but before he transforms. If Tails clears Launch Base Zone after hitting an S-Monitor at any time during the game, his ending sprite gains Sonic's palette, giving him a golden glow. (See left.) His Ring counter never drains and clearing an Act won't make him lose his invincibility or stop the Super Sonic music from playing, but going into a Special Zone or Bonus Stage will. Entering a new zone also removes the invincibility and restores the music if a musical silence is called, but he still has the ability to destroy breakaway objects by walking into them.

Trivia

 * This is so far the only super transformation Tails has displayed in the Sonic the Hedgehog series.
 * In Sonic the Hedgehog 2's VS Mode, if "Super" Tails clears an Act and Sonic happens to be using his Super palette, the normally blue background of the signpost will be affected by the palette and will glow yellow. This also applies to Sonic 3 since, whilst Tails remains unaffected by the palette change, items that normally are will be.
 * The legitimately obtained Super Tails in Sonic 3 & Knuckles cannot destroy non-Knuckles barriers automatically, not even in the Sonic 3 - Limited Edition prototypes where this form would be considered his "Hyper" form.
 * A representative from Sega has reportedly said that Tails was unable to transform with the Chaos Emeralds and needed the greater power of the Super Emeralds due to his younger age.
 * In Sonic the Hedgehog 3 & Knuckles, Tails originally was planned to transform into Super Tails with just the Chaos Emeralds. In some prototypes of a cancelled version of Sonic 3 & Knuckles called the 0517 prototype, Tails could do this, and Tails could even transform into Hyper Tails with the Super Emeralds. The only difference between the early Super Tails and Hyper Tails is that Flickies did not follow the original Super Tails. Before the game was finally released, it was decided to drop Super Tails since Tails could not use the Emeralds in Sonic the Hedgehog 2, and renamed Hyper Tails to Super Tails.
 * Super Tails is one of the few added features in the 2013 mobile re-release of Sonic the Hedgehog that was not carried over to Sonic the Hedgehog 2.