It pays to listen to what others have to say, whether it's an opinion on what they want to try, or an important suggestion of what you need to try.
As Sid points out, it's good to ask permission before you give the go-ahead on what you want, especially if it involves intruding on someone else.
Chekhov's Gun: Cassie's umbrella used at the gang's picnic at the beginning comes in handy near the end, when the roof is not strong enough to hold off the purple goo and they use the umbrella to protect them.
You Can Talk?: Emmy and the others to Sid Sycamore, after hearing him talk to them for the first time.
