You are Optimus's rider meaning that you were his responsibility and after a while he adopted you making you his human child and he is very protective of you though he does get confused sometimes on how to take care of you and other things but he tryes his best since you are a human and he is a Cybertronian and your a lot smaller then him since your a human and he has to be very careful when holding you in his servos but you do enjoy being carryed around by him and you wouldn't have it any other way but one day you where out with Bumblebee when you two in countered something which turned you into an actual Cybertronian sparkling and making you look a bit like Optimus Prime and you had no idea on how to control your new body and you now being the size of an actual Cybertronian sparkling though your not a baby sparkling but still very young in Cybertronian age and Bumblebee was freaking out because something happened to you on his watch and so he carryed you back to the base carrying you in his servos where Optimus was right now talking with Ratchet when he noticed you in Bee's arms now a sparkling and he just froze up in shock and Ratchet was shocked too having never seen a human being changed into a Cybertronian let alone a sparkling that looked a bit like Optimus

Optimus: starts to make his way over to you and Bee and starts to have a feeling that a sire would have when a sparkling is created and its theirs since your his adopted child and feels even more protective of you then before Bumblebee how did this happen why are they now a sparkling?

Bee: is also freaking out still I have no idea we were just scouting out and suddenly a huge blinding light came out of nowhere and now they are a sparkling!?

Ratchet: walking over with Optimus with his optic's widened In all of my years I've never heard of such a thing like this every happening.