Jurassic World Camp Cretaceous, Season 3, Episode 2
At about 9:30:
Brooklyn: Remember to keep an eye out for Kenji. I wouldn’t put it past him to scare us again.
They were trapped in an island with deadly dinosaurs. Kenji pretened to be a dinosaur and scared Brookly and Darius a few times. Now they are in a fog, looking for something to fix their boat, and Brooklyn said this.
‘Keep an eye out for something’ means that you scan an area for something you want. For example, you are going to a hotel, but you don’t know where it is. Then you ask your wife to keep an eye out for the hotel. If you are a police officer on a stakeout, you have to keep an eye out for anything suspicious. Here, they know where Kenji is. They don’t need to look for him. They need to keep an eye out for something to fix their boat, and keep an eye out for him (he might hide somewhere, waiting to scare them again) when they are searching for it. This use strikes me as odd. I guess I just have so much to learn.
I wouldn’t put it past him (to do sth) means that it’s not surprising he is going to do it. Here, Brookly means that Kenji would try to scare her and Darius, “I wouldn’t put it past him to scare us again”. The meaning of the phrase isn’t clear by itself, but it seems children in their teens are supposed to understand it. It’s difficult for me for sure.
https://dictionary.cambridge.org/dictionary/learner-english/i-wouldn-t-put-it-past-sb-to-do-sth