Ukuleleman is an unknown alien that appears in Season 2, Episode 2.
Ukuleleman was born out of trees from a swamp planet through unknown means. As the only one of his race, he became extremely lonely and tried to interact with those who visited his planet. Unable to smile, let alone make any facial expressions whatsoever, visitors quickly turned away. Due to his strange power of freezing people into smiling statues with his ukulele, he was able to keep them from leaving. This as well as his other ability to possess the frozen statues resulted in him becoming a "smile aficionado", collecting smiling statues so that he can one day find the perfect one and use it to get others to like him.
One day, however, he observed Dandy partying at BooBies and believed he had found the perfect smile. There after he sent Dandy a letter claiming to be a rare alien who was his biggest fan and requesting he come visit him at his party he was throwing at his mansion.
Dandy believed that Ukuleleman was in fact a beautiful alien woman and immediately proceeded to head to his mansion. Upon hearing that Ukuleleman was in fact the one who sent the letter, Dandy quickly left the building before he could be frozen. On his way out, however, he noticed that QT and Meow had been frozen by Ukuleleman for their smiles earlier that day when they had arrived to find Dandy who had won the "Mr. Misunderstanding Grand Prix" and needed to be in person as the crew was awarded the prize which was "a whole lot of food".
Angered by Ukuleleman's actions, Dandy stated that he would never smile again and after a failed attempt to freeze him, he quickly picked up his friends and escaped in his ship and headed to the nearby River of Time which would allow him to send his friends back to a time when they weren't frozen. After Dandy threw them in the river and proceeded to pick them back up, Ukuleleman materialized out of nowhere and tried to freeze Dandy once more.
Since Dandy stated that he would never smile again, Ukuleleman decided to freeze a smiling Dandy from the past by pulling a past self of Dandy out of the River of time. As he was doing this, Ukuleleman told of how if he froze the past Dandy, then the present Dandy would disappear but stated that there was no other way.
As he pulled the past Dandy out of the river, present QT and Meow grabbed on to him and were pulled out as well. With the present Dandy starting to disappear, he proceeded to jump on the rope pulling his past self and ran up to Ukuleleman and punched him in his mask, breaking it and killing him.
Dying, Ukuleleman burst into flames and told of how a smile would not have suited him anyway. Despite that, Dandy told him that he was smiling and that it was a great one at that. At peace with himself, Ukuleleman dropped his ukulele and was completely engulfed by flame. Catching the instrument, Dandy started to play it.