Princess Bubblegum

Princess Bonnibel "Bonnie" Bubblegum (often called PB and on occasion Peebles, P-Bubs, or other nicknames) (voiced by Hynden Walch) is a main character and the most recurring Princess on the series Adventure Time, and first appeared in the animated short. She is a scientist, inventor, and the ruler over the Candy Kingdom. She was outvoted by the King of Ooo in "Hot Diggity Doom" and later quit, until a rebellion against King of Ooo allowed her to reclaim the throne in "The Dark Cloud." According to the events in "Princess Day," during her first rule over the kingdom, she was considered a registered princess. In "The Dark Cloud", she regained her status as princess near the end, as seen in the song "Everything Stays". As revealed in "Elemental," she is the current Candy Elemental. Princess Bubblegum is one of the minor deutergonists of the Yuna's Princess Adventure franchise.

Finn the Human
When Finn the Human has a crush on Princess Bubblegum, she always being a girlfriend to him.

Princess Twila
When Princess Twila was a baby, Princess Bubblegum always babysits her anytime. When Twila has a temper tantrum, PB calms her down by soothing her. Years went by, Twila grown into a filly and best bonds with PB.

Princess Lilly Sparkle Rose
Princess Bubblegum always babysits Lilly (as a young filly), along with Twila (as the baby), they love to color on the coloring books. Years went by, Lilly always help PB with her baby brother, Prince Flashlight.

Nyx
When Twila introduce Nyx to Princess Bubblegum, she was happy to meet her. When Nyx feeling very sad about her deceased parents, she tells PB about how they got killed by Kylo Ren, Captain Phasma, Darth Vader and the First Order Stormtroopers. So, PB comforts Nyx by hugging and wipes the tears away from her eyes and cheers her up.

Prince Flashlight
When Prince Flashlight was born, Princess Bubblegum was happy to see him. One month later, PB begins to babysit Flashlight for the very first time ever with Twila's help by playing, cuddling, feeding, bathing and napping him. PB always giving Flashlight new toys for Hearth's Warming and Christmas.

Princess Yuna
When Princess Bubblegum was hired to be the new trainer, Princess Yuna always love her. PB helps Fizzlepop Berrytwist, Grubber and Phil by training the foals and children to fight and race. Yuna gives PB a medal that she made and it says "Best Trainer Ever" and she loved it while hugging Yuna.

Trivia

 * Princess Bubblegum will first meet Princess Yuna and her friends and will become the third trainer for them in Yuna's New Sibling Part 1 and 2.
 * Princess Bubblegum was also Princess Twila and Nyx's babysitter.