It was the main driving point in Operation: H.O.M.E. when Numbuh 3 brought it along with her, while her sector was on a mission. When they were supposed to capture Count Spankulot, but escaped when My First Rainbow Monkey was slapped on its butt and tore apart. Then the team had rushed to Numbuh 3 as she screamed.
Upset the next day, Numbuh 3 stayed up in her room and tried to sew her doll's butt back with a heart-shape button. Numbuh 1 come in and cheered her up after scolding her for letting Count Spankulot get away, trying to convince her to give up the doll. Numbuh 5 attempted to cheer her up with Rainbow Munchies (with 20% more sugar) when her leader failed when Numbuh 3 spotted an ad for Rainbow Monkey Retirement Home.
After visiting the estate, Numbuh 3 said an emotional good-bye to her First Rainbow Monkey and left with Numbuh 5, who tag along with her. Numbuh 3 started to freak out the next after seeing a heart-shaped button (the same one she used to sew onto her First Rainbow Monkey earlier in the episode) in her rainbow munchies, because she thought there was something wrong with him and dragged Numbuh 5 along with her.
It turns out Nurse Claiborne (from Operation: P.I.N.K.-E.Y.E.) had shredded it to make Rainbow Munchies taste better by making it out of real Rainbow Monkeys, but she sewed it back together (forced by Numbuhs 3 and 5), along with the rest of the Rainbow Monkeys as Numbuh 3 happily reunites with it.
My First Rainbow Monkey is a light-purple colored Rainbow Monkey with a long white a beard, pink glasses, and it is tattered a little bit due to its elderly form.
- It is ironic that the Rainbow Monkey aged, as almost no other Rainbow Monkeys have been shown to age.