Hi, there!
I watched it as a child, so it should be from 80s/90s. I think it was a TV series, but could have been a movie or a commercial too. I recall the real human was taking that 2D character(who was so small, it was fitting in his open hand) and putting him in his backpack to take him to school.
I am not sure, but I think it could be that the boy drew that 2D character and it unexpectedly became alive for some reason, like jumping out from the drawing.
I just recently learnt about Mandela Effect and I want to find all the series and movies that I can recall.
Sounds like McGee & Me: https://en.m.wikipedia.org/wiki/McGee_and_Me!
It is!! This is solved!
Thank you!
You're welcome! It's just luck & the grace of God that someone heard of the series.