Alien Husband

Tree Trunks' Alien Husband makes his first and only appearance in "High Strangeness." It is seen that he occasionally visits Tree Trunks and will randomly transport her to his home planet and that they have several hybrid children together. However, Tree Trunks is quickly returned home.

Later in the episode, Princess Bubblegum sets off a rocket that resembles her countenance into the sky. Seconds after it flies into space, Tree Trunks is abducted by aliens, who point out the rocket that has crashed into their realm. The rocket head opens to let out streams of candy matter, which begin to invade and attach themselves to the aliens' bodies. Tree Trunks is transported back to Ooo, and she immediately berates Princess Bubblegum for hurting the aliens. Princess Bubblegum is surprised that Tree Trunks knows the rocket went into space, but insists she does not know what she's talking about. Later, Tree Trunks and PB are both transported to the alien world.

Princess Bubblegum apologized as she intended to seed new Candy Kingdoms on uninhabited if something catastrophic were to happen to Ooo. The Alien husband then agreed to fly Princess Bubblegum's probes to his abandoned home planet so they can start their new Candy Kingdom, but the galaxy is so far away, he will not be able to see Tree Trunks again for another 40 years.

Appearance
The Alien husband is a slim alien with  gray skin and big greenish-black eyes

Trivia

 * Princess Zip, a character in the far future highly resembles him, suggesting his species will eventually settle on Earth.