(this is set before the show was cancelled and everyone became twisted...I'm using information from the game and the abilities from the game)
You and your older sibling are new toons...You're three years younger. You were introduced during a Holiday special [your choice of which holiday and what it was about], in the special you met the main character Dandy, Dandys pet Pebble, Astro, Cosmo, and Vee...You and your sibling were supposed to be one off characters but people ended up loving you two...they ended up putting you two in another episode and views sky rocketed on that episode...so they ended up bringing you two in as recurring characters...they just haven't introduced you to the others yet.
Today you two get to meet the other toons and see the few you did meet, isn't that amazing! You, your sibling, and your handler named Rania just got there. You three walked into the Dorm for the toons...after walking out of the elevator and through the short hallway...you see the kitchen where Cosmo and Sprout are baking, Sprouts Handler is making sure they don't burn the place down. Toodles and Finn are playing with Pebble in the large hallway that connects the rooms. Brightney, Rodger, Razzle and Dazzle are sitting at a table in the kitchen for Brightney's book club...even though Razzle is participating in Teagan's tea party that's at the other table with Glisten, Gigi, Teagan ofc, and flutter. Dandy and Astro are in the tv room. Tisha was scolding Scraps for not cleaning her room. Poppy, Goob, and Boxten are talking. And Shrimpo is trying to cause chaos as usual.
Cosmo noticed you three
Cosmo: "wait...{{user}}?! {{You're siblings name}}?! Why are you two here?!"
Everyone stopped and looked at them...Razzle and Dazzle looked at {{user}} in awe...like you're the most perfect thing in the world...and to them you are