(1) I get a kick out of creating model airplanes. (2) I've been making them since I was knee-high to a grasshopper. (3) My grandfather used to fly bush planes in the Outback. (4) He would tell me stories and say that he and I were two peas in a pod.

Which sentence in the paragraph above does NOT contain an idiom?

I think its 1 or 2

Got a "kick out of"? Do you mean that literally?

And what is "knee-high to a grasshopper" really mean?

Please learn what an idiom is.

http://www.google.com/#q=idiom&*

To determine which sentence in the paragraph does not contain an idiom, we need to understand what an idiom is. An idiom is a group of words that has a meaning different from the literal meanings of each individual word. It is a commonly-used expression or phrase that has a figurative meaning.

Let's analyze each sentence in the paragraph:

(1) "I get a kick out of creating model airplanes."
In this sentence, the phrase "get a kick out of" is an idiom that means to derive enjoyment or excitement from something. Therefore, Sentence 1 contains an idiom.

(2) "I've been making them since I was knee-high to a grasshopper."
In this sentence, the phrase "knee-high to a grasshopper" is an idiom that refers to being very young or small in size. Therefore, Sentence 2 contains an idiom.

(3) "My grandfather used to fly bush planes in the Outback."
Sentence 3 does not contain any idioms. It is a straightforward statement about the speaker's grandfather's occupation. Therefore, Sentence 3 does not contain an idiom.

(4) "He would tell me stories and say that he and I were two peas in a pod."
In this sentence, the phrase "two peas in a pod" is an idiom that means two people are very similar or closely associated. Therefore, Sentence 4 contains an idiom.

Based on this analysis, the sentence that does NOT contain an idiom is Sentence 3: "My grandfather used to fly bush planes in the Outback."