Was Lyanna Stark the Knight of the Laughing Tree?

The Knight of the Laughing Tree was a mystery knight who fought at the Tourney at Harrenhal. He defended the honour of Howland Reed by challenging and defeating three knights whose squires had bullied him, demanding that they chastise the squires in order to ransom back their horses and armour.

The Knight of the Laughing Tree is so-called because of the blazon on his shield, a smiling heart tree. His true identity remains unknown.

But is it possible for the mystery man to be a woman? Lyanna Stark?

Maybe...

Howland Reed found himself bullied by three squires, none older than fifteen-years-old. He had already "grown to manhood", but the boys were all larger than him in size. His only offensive weapon, a three-pronged spear, was easily snatched away by his opponents. He was then thrown into the ground. His assailants repeatedly mocked him, shoved him, and kicked him. Help arrived in the person of Lyanna Stark ("the she-wolf"), who shouted indignantly that Howland was her father's bannerman. She beat off his attackers with a tourney sword, scattering them away.

Lyanna then took him back to her "lair", probably a tent. She cleaned his wounds and bound them with linen, then introduced the guest to her brothers Brandon Stark, Eddard Stark and Benjen Stark. That evening, Lyanna persuaded the crannogman to attend the feast marking the start of the tournament. She insisted that he was highborn and had as much right to attend as anyone.

Late on the afternoon of the second day, a mystery knight "short of stature" appeared in the lists. His armour was made up of mismatched armour bits and pieces that appeared ill-fitting on him. His shield was blazoned with the image of "a white weirwood with a laughing red face".

The mystery knight challenged and defeated all three of the previously mentioned knights, winning custody over their horses and armour. None of them were particularly popular, so the smallfolk cheered for the mysterious "Knight of the Laughing Tree". When the defeated trio sought to ransom back their former property, the knight declared his terms, that they ought to teach their rude squires honour. His voice sounded "booming" through his helm. The trio proceeded to chastise their squires sharply.

Could Lyanna have gotten revenge for Lord Howland in the form of the Knight of the Laughing Tree?

What we know about the Knight:

• The mystery knight must have been someone who knew about Howland Reed's experience with the squires and was motivated to avenge him.

• His height was below average.

• The mismatched armour would point to the Knight not having access to regular armour, or having regular armour with tell-tale markings on it.

• The booming voice was most likely not the regular voice of the Knight.

• The Weirwood image implies a connection to the Old Gods and the North.

• He was competent enough at the joust to defeat three knights who had made it through the first day of the tourney, but as none of them were particularly well-known, he need not have been unusually skilled.

• Meera Reed was surprised that Bran had never heard the story before, which suggests that the Knight may have been either a Stark, or someone close to the family.

Eddard compares his tomboyish daughter Arya to Lyanna in both appearance and personality, adding that Lyanna probably would have carried a sword if their father had allowed it. Lyanna is consistently noted to have been an extremely skilled rider. She also seems to have had an interest in swordfighting, and is shown to have been capable of outfighting Benjen during their childhood. Horsemanship skills are necessary for jousting and "riding at rings" is standard training for squires, preparing them for actual jousting. Lyanna using the same exercise in her horse-riding training would not be impossible. Benjen could have provided armour for her, as he offered to do for Reed. As an underage girl, she could be shorter than the average man. Provided she had the necessary skill and some luck, Lyanna could defeat three knights of uncertain ability. (The best jousters don't seem to have competed prior to the final day of the Tourney at Harrenhal.) In jousting, "the speed of the horse provides the force of the attack", not the physical strength of the rider. The theory would also explain how she met Rhaegar Targaryen, the man charged with finding the Knight. And the same man who crowned Lyanna as his Queen of Love and Beauty. They had no known previous interactions.

Negative points of this theory would be doubts concerning the skill and youth of Lyanna. The existence of swordfighting and riding skills doesn't necessarily confirm the existence of jousting skills. In her fight with the squires, there would be other factors on her side. There is no mention the squires were armed. There was likely an element of surprise at work, when they found themselves under attack. If they recognized their assailant as a noble girl, they may have consciously avoided hurting her to avoid the wrath of her House. None of these advantages would be present on the jousting field. Even if she had actual training, this would be the first real test for her skills. As a novice in the sport, her victory would be far from guaranteed. Lyanna would have logically tried to sound like a man, but the helm would not be enough to produce a powerful voice.