The Tango Beast was a minor character in "Episode XLV: Scotsman Saves Jack, Part 1."
The Tango Beast is a mythical creature confronted by Jack some time before the episode he appeared in. He is a green, dragon-like creature with light-blue rings of fur around his neck and tail and a pink snout. He is mild-mannered and docile on a good day, but he hates the scent of the "Wily Jub-Jub plant" more than anything else in the world. One whiff sends him into an angry, mindless frenzy.
The Tango Beast was terrorizing a town one day, which led to a confrontation with Samurai Jack. The Tango Beast managed to leave a scar across Jack's chest, but was ultimately defeated. After the fight, Jack sat him down for a heart-to-heart chat. With Jack's help, the Tango Beast realized that his actions were the result of trying to make himself feel better about his low self-esteem. He was inspired to get his life back on track, and Jack went on his way.
Later on, Jack had suffered amnesia, believing himself to be a normal man named "Brent Worthington." The Scotsman was trying to restore Jack's memories, and retraced his steps to the Tango Beast's cave after seeing the scar the beast had left. After lulling the Tango Beast into one of his frenzies with a Wily Jub-Jub plant, the Tango Beast burst out of his cave roaring angrily. The sight of this beast caused "Brent" to faint. The Scotsman brought the beast back to his senses with one punch and interrogated the frightened creature. The Tango Beast recounted his recent encounter with Jack and pointed the Scotsman into the direction Jack went in after they spoke with each other.
After his fight with Jack, his life seems to have improved. He has his old job back, is more outgoing, and claims to have improved his hygiene. That last one seems debatable, as the Scotsman still thinks his stench could knock a man out cold.
It is unknown how the past Aku's destruction affected his existence.