I think it's important to remember that this is an intercultural conversation. That fact is blindingly obvious to the interlocutor. And let's face it-- people use their own cultural stereotypes to interpret meaning in this situation. If Japanese people have "seen" anglophones use these phrases in movies, then it'll probably fit right into their expectations when talking to a real-live anglophone. Sometimes Japanese people get really uncomfortable if anglophones behave "too Japanese" in their presence.
Or maybe I just am bad at it, and end up over-doing it? But I'm sick of saccharine condescensions like "You're more Japanese than me!" "You understand the Soul Of The Japanese" (gotten that one three times and it makes me want to punch someone)
Even if the OP's words are in Japanese, I'm guessing the OP has an accent, and hasn't exactly perfected Japanese non-verbals like body language and tone of voice. I've heard people say that the majority of communication is non-verbal-- well, the OP's words might as well match what his/her body already betrays. Because let's face it, "tondemonaidesuuuu" probably sounds like a stale script when this person says it. Because it is. And I have to use every ounce of my body and voice to pretend that it isn't a stale script when I say it every day.
When you live in a foreign culture, you get to reinvent yourself in the new language-- you have to, because your Japanese persona can't be the same as your native one. However, it can be hard to live a perfectly Japanese persona day-in, day-out. Everyone else assumes that you, an anglophone and a foreigner, are egotistical and easily flattered. Saying "mada mada" won't change their minds. So it's okay to make your Japanese persona a little more liveable by injecting it with your own native rhetorical norms.
Who knows. You might even look like a movie star to them. ;)