- "Take her to the moon for me, okay?"
- —Bing Bong's last words
Bing Bong is the tritagonist of Inside Out.
Bing Bong is Riley's imaginary friend that exists within her mind. He was created by her when she was 3. As a result, he is somewhat naive in both his appearance and personality. For instance, he does not know how to read. Bing Bong's body is mainly made of cotton candy. Shape-wise, he is part cat for the tail, part elephant for his trunk, and part dolphin, though the latter is not so obvious. He cries candy when he's sad.
Riley used to play with Bing Bong in all sorts of games when she was 3. However, she stopped when she was 4, and since then, Bing Bong has been out of work and errant. He mostly stays around Imagination Land, collecting happy memories he likes in a bottomless bag.
He greatly misses the time when he was best friends with Riley, and is desperate to not be forgotten. Bing Bong's last link to Riley is his "rocket", a wagon that was meant to take Riley to the moon. It runs on song power, meaning its rainbow rockets light up when his song, "The Bing Bong Song", is sung.
After Joy and Sadness are ejected from Headquarters and get lost in Long Term Memory, they stumble upon Bing Bong. He is initially afraid, but when Joy presents herself, he is thrilled to meet her. Bing Bong, who has been forgotten by everyone for a long time, is more than happy to help them, more so when Joy tells him she will put him back in business when she gets back to Headquarters. He proposes that they take the Train of Thought that will lead them directly to Headquarters, and shows them the way.
He leads Joy and Sadness to a dark room, which he thinks is a shortcut, claiming that the scripture above the door reading "D-A-N-G-E-R" means "shortcut". However, as soon as the three are inside, the room closes and reveals itself to be Abstract Thought, a place that reduces everything to abstract concepts. Bing Bong and the others escape, but when they get out, the Train of Thought has left.
Bing Bong leads them to the second closest station, at Imagination Land. As they are there, they witness drastic changes in what Riley thinks about, with more childish things being toppled down. In the process, Bing Bong's precious wagon is thrown into the Memory Dump, which puts him in a profound despair. Joy tries to cheer him up in vain. Then, Sadness talks to him, and by getting him to express his sadness, comforts him. Bing Bong, happy again, brings them to the Train of Thought.
However, the train stop as Riley goes to sleep. Bing Bong, Joy and Sadness go to Dream Productions to try to wake up Riley. They bring the dream currently being filmed in total chaos. Bing Bong shows himself to try to remind Riley of him, but he is arrested and imprisoned in Subconscious. He is rescued by Joy and Sadness, who also free Jangles, one of Riley's worst fears, to wake her up.
The three of them finally board the Train of Thought. Bing Bong finds on board a recent memory from Riley, and is surprised to see how she has grown, concerned that she won't fit in his wagon. However, the train is quickly destroyed by the destruction of Honesty Island. Bing Bong then falls into the Memory Dump as he was trying to catch Joy, while Family Island crumbles down. There, he is terrified to see that he is slowly fading and on the verge of disappearing. He meets with Joy who has also fallen in the dump.
Together, they decide to use Bing Bong's wagon to blast off out to the surface. They sing as hard as they can, but they can't get high enough. They then try again, but still don't make it. As Joy is starting to lose courage, Bing Bong asks that they try one more time. This time, sacrificing himself so that Riley can be saved, Bing Bong lets go and falls back down as the wagon takes off, letting Joy succeed to reach the top in the now lighter cart. Bing Bong, happy to have been helpful again, makes his final goodbyes to Joy, and, accepting that his time has passed, fades away.