Welcome back from the ocean haha!
I haven't seen this movie in a while actually, but it's one of my favorites!
1. Okay, there was a song dedicated to imaginary friends. The gang clearly has a differnent mind set unlike other dino children. But from what I remeber, Petrie had an imagenary friend becuase he wanted someone who could agree on whatever he said, and having an imagenary from was basically for the benifit of himself. In the end, I guess they realized that true friends were already with them.

2. I think Mo was one of the highlights of whole movie. He has a cute and fun personality! Alos I think he's one of the few marine creatures that actually talk in the franchise, other then Eli I guess. Mo is just this little prehistoric dolphin that everyone loves, although I understand how people find him annoying. Glad he made an appearance in the series though!