Timon and Pumbaa meet Bigfoot. When they accidentally eat Bigfoot's bug friends, Bigfoot makes them keep him company so that he won't be lonely.
"Bigfoot, Littlebrain" begins by introducing Timon, a meerkat, and his warthog friend, Pumbaa.
At the start of the episode, a bored Pumbaa is lying on the ground, stating that he and Timon have been doing nothing for three days. Timon sees an article from a magazine about Bigfoot, much to Pumbaa's excitement as he tells his friend that Bigfoot is his hero because he is big and scary and does almost nothing just like them. The warthog suggests that he and Timon go on an adventure to find Bigfoot. Timon somewhat doesn't accept it until he sees bugs flying over Bigfoot's head.
Timon and Pumbaa go on a journey to find Bigfoot. As the two do so, they see rocks coming towards them and they quickly get out of the way. Later, Timon and Pumbaa see Bigfoot's trails and follow it until Timon falls in a big foot-shaped hole. After Timon gets lifted up by Pumbaa, Bigfoot shows up and Pumbaa is happy to meet him. Bigfoot asks Timon and Pumbaa if they want to be his friends and the two agree and they eat the bugs that are flying over Bigfoot's head.
After eating the bugs, Timon and Pumbaa get ready to leave to go on their next adventure, but Bigfoot wants them to stay with him otherwise he'll be lonely. He reveals to Timon and Pumbaa that the bugs they ate were his friends, much to the two friends' shock. While Timon still wants to leave, Pumbaa suggests that they should keep Bigfoot company. Bigfoot decides to play a game of "swat" and he swats Timon. Therefore, Pumbaa suggests they should play a different game and Bigfoot decides to play hide-and-seek. He hides Timon in a trunk of a tree and looks for the meerkat because he forgot where he hid him. Timon gets out of the trunk and wants to go back home to Africa, but Pumbaa suggests that they should stay, seeing how happy Bigfoot is with his new friends.
The next morning, Timon tells Pumbaa to sneakily escape Bigfoot, but Pumbaa still wants to stay with him. Bigfoot wakes up and plays two different games with Timon and Pumbaa, which causes some chaos. Pumbaa now starts to agree with Timon, saying that they should do something. Timon gets an idea. He goes to Bigfoot and makes him stare at a line he drew on the ground. Timon gets ready to leave while Bigfoot is distracted by the line, but Pumbaa suggests that before they do so, they should find a new friend for Bigfoot.
Timon and Pumbaa go catch some bugs for Bigfoot to befriend. After doing so, the two go back to Bigfoot, who is still staring at the line on the ground, and try to get his attention. Then, a butterfly shows up and befriends Bigfoot, who now lets Timon and Pumbaa go since he now has a new company. While Bigfoot and the butterfly walk off, Timon and Pumbaa are about to eat the bugs they caught, but the bugs start chasing the two friends.