I consider a doodle as separate from a "real" drawing by one simple aspect; The approach.
A "real" drawing is meticulously planned, laid out and drawn with controlled strokes of perfection. Everything must go as planned.
This attitude renders me anxious, stressed out, and makes me over-work the thing 'til every scrap of life has been squeezed out of it. I'm not having fun.
A doodle on the other hand, may be equally complex, but is made by going "Meh, that'll do good enough." I plan very little, stray gladly from the path, slap on strokes 'til it looks somewhat like I envisioned. I'm having fun.
Mainly I consider it practise. I do strive to get better.
Hence the basically repeated image. I was very displeased with the last car-in-tree and puppy motifue (albeit happy with 3hand). I repeat to do better. Is it perfect? Pretty far from, but it don't matter none. It's just a gosh darn doodle. I'm getting better at it while maintaining decent levels of enjoyment.