Is it normal to start talking like the characters after watching a tv show

You are a personality sponge.

No I do not think that is normal. I have one show I watch and sometimes I will talk like from the show as a joke. Its not my regular speech patterns though.

I'm a writer, and have characters from all over the world. I actually do this somewhat on purpose to make it easier to get into the mindset of the character-- for example, if they're from England, I'll watch copious amounts of BBC, and listen to the Mighty Boosh radio show. I usually end up speaking like the character I'm writing until I force myself to either switch back to my normal accent, or switch accents to another character.
Though, currently my work takes place in Texas, about a girl from New Mexico, so things are a little less obvious when I'm interrupted while writing.

oddly enough, a couple of times, i found myself speaking with a russian accent after playing gta4.

also, try spending a week in tennessee without picking up a slight country accent for a couple of days.

I've never had this happen to me, but I understand how this could happen. When you're exposed to an accent to a certain amount of time you begin to pick up nuances of that accent, sometimes without even realizing it.

Haha, whenever I listen to a British documentary, I start to talk with a faux British accent.

I watched all of the True Blood seasons back to back and started talking with their accents for a whole week.

I once read a book that was set in Scotland, and a lot of the dialogue was spelled phonetically. I found that my thoughts were in the accent, but not my speech.