Hey guy's this plot bunny came to me in my sleep. I have not watched or read 'Attack on Titan' and didn't want hurt the fans of the series but I didn't want this plot bunny to die so here it is...
Harry Potter is a dwarf Titan baby that Eren or one of the other human/titans found and placed in a freeze time vault with info of what he is. The vault was forgotten until James and Lily Potter accidentally opened it. They took Harry as their son since Lily couldn't have kids. Sirius and Remus are the only ones that James and Lily told what Harry really was.
Please don't let this plot bunny die and good luck to everyone that takes the challenge!