Same shit happened to me once about a year ago except I was stuck in the middle. The two fatasses ate junk food the entire time and it was a full flight
Sorry to hear OP but as already mentioned, you should have said something on the spot. Airlines should have markers for manatee's just like they do for luggage. If the luggage doesn't fit in the small metal crate then it gets checked. If the manatee doesn't fit in the seat, it should get checked as well..
im hopefully coming home next month on leave from Germany and I better not get stuck next to some blimp for my 8+ hours flight. thankfully my wife is sitting next to me and shes tiny, but the other side of me god only knows.. last time thankfully KLM hooked me up with first class for being a Soldier I was shocked I loved it. but I know that wont always happen. wish me luck lol.