Several short stories are mentioned in MBH. They are given here just for information --

(1) MBH, Van/14 - Story of Manakanakaa Rishi
When Arjun had gone to obtain Divine weapons from Indra, one day Pulastya Rishi came and advised Yudhishthir to go on Pilgrimage and told him about all the Teerth, they should visit. Among then he named one Teerth as Sapt Saaraswat Teerth. he told about that Teerth that there the sage Manakanakaa got success in asceticism. It is said that once the sage Manakanakaa cut his hand by the blade of Kushaa grass. He was surprised to see that the vegetable juice came out of his hand instead of blood. He began to dance seeing this. Seeing him dancing all mobile and immobile creature also started dancing with him. Seeing this all Devtaa and Rishi went to Mahaadev and said to him - "Do something so that he does not dance like this as dancing ,like this doesn't look nice for him."

So Mahaadev went to the Rishi and asked him - "Why are you dancing?" Manakanakaa said - "I am the Rishi who has earned lots of Punya. Can you see that vegetable juice is flowing from my hand? That is why I am happy and dancing." Hearing this Mahaadev Jee said - "I do not wonder at this at all." and he pressed his thumb with his own finger and Lo, there came out white ash from the wound made there. Seeing this Muni got ashamed and fell on Mahaadev's feet. Considering that nothing is greater than Rudra he started praying him - "You are the greatest, you have created everything, and only you destroy everything at the end of the world. Even gods cannot know you, how can I know you? O god of gods, grant me your grace." Shiv got pleased with his prayer and said - "Let your asceticism increase thousand times by my grace. I will stay with you here in your Aashram, Who will take bath here in Sapt Saaraswat Teerth, they will attain everything here and thereafter." and Mahaadev Jee disappeared from there.
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Draupadee in her previous birth was Indrasenaa, the wife of Sage Maudgalya. Due to leprosy her husband died early and in order to satisfy her desires she prayed Lord Shiv with great devotion. When Shiv appeared and asked what she wanted, she got bewildered and asked five times for a husband. Lord Shiv blessed her with five husbands in the next birth. That is why she got five husbands in her next birth as Draupadee.

Its another version is

Dhritarashtra in his previous birth was a tyrant king, who one day saw a swan surrounded by hundred cygnets. He ordered to poke the eyes of the swan bird and kill all the hundred cygnets just for pleasure. Therefore, in next birth he was born blind and all his sons were killed in the war.
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The chariot that Krishn drove for Arjun was very powerful. After the Mahaabhaarat war  was over, Krishn asked Arjun to dismount the chariot first. After Arjun, Krishn got down from the chariot, and as soon as Krishn got off, the chariot exploded. Arjun asked Krishn - "Krishn, What happened." Krishn told him that the chariot was already in its broken condition, only because of Him it was in working order. And for the same reason I asked you to get down first."
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Paandu was a learned man. His last wish was that his sons must eat his brain after his death so that his children can get all his knowledge what he might have. However, Sahadev was the only one who followed the instructions of his father. With the first bite, he became enlightened about all that had happened in the history. With the second bite, he became enlightened about all that was happening in the world. And with the third bite, he became enlightened about all that would happen in the future of the world. And that is how he became Tri-Kaalgya (knower of the three times)

Sahadev knew everything about the future. He knew that a war was going to occur but he kept silent because he was under a curse that if he revealed anything to anybody he would die.

Sahadeva desired Viraat to be the General of the Paandav army, but Yudhishthir and Arjun opted for Dhrishtdyumn.
The flag of Sahadev's chariot bore the image of a silver swan.
He had taken an oath of slaying Shakuni and accomplished this task successfully on the 17th day of battle.
After the war, Yudhishthir appointed Sahadev as his personal bodyguard.
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Some believe that Abhimanyu was actually the soul of a demon named Kaalayavan. Krishn burnt Kaalayavan to death, captured his soul and tied him in a knot of his upper cloth. He took the demon spirit to Dwaarakaa and stuffed him into a cupboard. Subhadraa (Arjun’s wife) accidentally opened the cupboard and a light entered her womb which made her unconscious. This was the main reason why Arjun revealed only half the process of Chakra Vyooh to Abhimanyu when he was in the womb.
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Eklavya was the son of Devashrava (brother of Vasudev) who got lost in the forest and was found by a Nishaad Hiranyadhanu. Eklavya died protecting his father during Rukminee Swayamvar. He was killed by Krishn. For his great sacrifice, Krishn blessed Eklavya that he would be reincarnated to take revenge on Drone so he took birth as Dhrishtdyumn.
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Lots of short stories including the Amrit Manthan are part of the original Mahabharata epic. Few people may know that the entire epic was narrated as a flashback at the Sarp Yagya performed by Janamejaya, the son of Pareekshit.
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Yudhishthir learnt to play dice form the Sage Brihadaashwa who narrated the story of Nal and Damayantee during the exile of Paandav.
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As it is believed that the war took place in Kuru Kshetra, there the soil texture is different in a particular 30 kilometer surroundings which puzzles scientists till today because the soil cannot attain such a texture unless it is exposed to 1000 degree Celsius of heat for a long time. This observation poses a question whether Mahaabhaarat is just a mythological story or did it actually happened in the past?
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Barbareek was Bheem's mighty grandson and Krishn’s pupil. Barbareek was invincible in war and had three arrows given to him by the Goddess Kaamaakhyaa. Using a single arrow, Barbareek could wipe out all enemies in his sight but Barbareek had sworn to aid the weaker side in war. This posed a threat to the Paandav because if Barbareek wiped out a large portion of the Kaurav army on the first day of the war, they would be weakened and thus Barbareek would be forced to join them due to his oath. So Krishn asked Barbareek for his head as "Guru Dakshinaa". Barbareeck as a disciple was obliged to obey.
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Vidur was the incarnation of Yam Raaj. Yam Raaj was cursed by Maandookya Muni to be born as a Shoodra because Yam Raaj punished him very severely just for piercing a small insect by a straw.
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Krishn once protested to Yudhishthir that why the king of Indra Prasth did not seek his assistance while playing the Dice game. If Shakuni could have played the game of dice on behalf of Duryodhan, why not Krishn could have played on behalf of Paandav?

At another time He said - "I did not know about this game, I was not in Mathuraa, I went to fight with Krishn Vaasudev, otherwise I would have surely come to Hastinaapur and this episode (Draupadee Vastra Haran) had not taken place.
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When Ved Vyaas Jee was suggested the name of Ganesh Jee as his scribe to write Mahaabhaarat, Ganesh Jee put a condition that he would not stop in between writing his book. At this Vyaas Jee also put his condition that he would not write any thing which he does not understand. Both agreed on these conditions and the writing of this epic began. Many verses composed by Ved Vyaas Jee were very difficult to understand for Ganesh Jee, . It is said that as Ganesh Jee could not write them witout understanding them first, he took some time to understand them and this break time allowed Vyaas Jee to create many other further verses. However, these verses are so complex that 80 per cent of them remain unsolved even today. There are 8800 such verses in the Mahaabhaarat.

Besides it is said that whe Ganesh Jee was writing Mahaabhaarat, his pen broke, so not to disturb his writing, he broke his one tooth and used it as his pen that is why he has one tooth - Ekdant.