Phrases of American Dramas

　When I was watching an American drama, I was noticed that I could understand some phrases or words without Japanese subtitles.

For example, "you're insane" and "creepy" in "The Big Bang Theory," "you're an idiot" and "you idiot" in "Dr. House," "damn it" and "put your hands on your head" in "24."

I might have a dirty mouse if I keep watching these dramas repeatedly.

However, it is interesting for me to know various characters' trademark phrases.

• Phrases of American Dramas
• Phrases from American Dramas

• When I was watching an American drama, I was noticed that I could understand some phrases or words without Japanese subtitles.
• While I was watching an American dramas, I was noticed that I could understand some phrases or words without Japanese subtitles.

  Putting "when" at the beginning somewhat implies you don't watch dramas regularly, or maybe not at all any more. From the rest of your writing, it sounds like you do still watch them, and using "while" better implies this. Also, you talk about multiple shows, so we'll pluralise "drama" here.

• For example, "you're insane" and "creepy" in "The Big Bang Theory," "you're an idiot" and "you idiot" in "Dr.
• This sentence is perfect! No correction needed!

• House," "damn it" and "put your hands on your head" in "24."
• This sentence is perfect! No correction needed!

• I might have a dirty mouse if I keep watching these dramas repeatedly.
• I might get a dirty mouth if I keep watching these dramas (repeatedly).

  "Repeatedly" is implied by "keep watching", so it isn't necessary.

• However, it is interesting for me to know various characters' trademark phrases.
• However, it is interesting for me to learn various characters' trademark phrases.

  Using "know" here makes it sound like this is an unusual thing for you to know about, but it's not uncommon to learn catchphrases even in other languages.

For the longest time, my Japanese was limited to mostly curses. Somehow they're just easier to remember.

• Phrases of American Dramas
• Phrases from American Dramas

• When I was watching an American drama, I was noticed that I could understand some phrases or words without Japanese subtitles.
• While I was watching an American drama, I was noticed that I could understand some phrases or words without Japanese subtitles.

• I might have a dirty mouse if I keep watching these dramas repeatedly.
• I might have a dirty mouse if I keep watching these dramas repeatedly.