What's the difference between '처럼' and '같이'?

I saw this question in one of language learning websites and so left a comment there.
Here is what I wrote :)

They are almost the same actually!
I will just give you some examples :)

~처럼
You act like a child! 너 어린애'처럼' 행동하는구나(after Noun)

or you can also translate this into 너 어린애'같이' 행동하는구나 (change '다' to '이' after Noun and before Verb)

In most sentence, you can substitute 처럼 for 같이.

~같다
She looks like a baby. 그녀는 아기처럼 보인다 or also can say 그녀는 아기같이 보인다.
but can also use this as a verb at the end of a sentence like this.

너 바보같다~ (in this situation, you can't substitute 처럼 for 같다. '너 바보처럼'..... and what? this is not a complite sentence, right? :P )