I'm the faithful-as-a-bird-dog type. I can't be devious.
5 seconds sound clip from the Desk Set (1957) movie soundboard.
You can hear this line at 00:19:55 in the Blu-ray version of the movie.
Quote context
[...]
- Mike's on his way to see me.
- Did you hear anything I said?
- Yes, darling, I heard every word.
- I'm the faithful-as-a-bird-dog type. I can't be devious.
- But when he disappears, remember, you heard it on this channel first.
[...]