I do so many of these - and DS2 is similarly afflicted. He does the 'tell me what you think about me' thing whenever he hears the word 'question' 
If I hear anyone shouting 'Hey you!' I have to follow it with 'the rock steady crew.'
If anyone says 'just say no' I break into the Grange Hill anti-drugs song, to which I inexplicably know all the words 
'Stop!' Has to be followed by Hammertime. I thought it was the law.
Ds1 voices one of our dogs brilliantly, and monologues him all the time.
If I fart, even on my own in the car, I have to say 'pardon'. It's like a reflex. But I've been doing it so long, I don't say the full word, I just do a kind of 'menem' noise under my breath. I feel wrong if I don't.
If I hear the word 'phenomenon' I have to follow it with 'do do do do do' like the Muppets song.
If I'm cooking on my own I sometimes pretend I've got my own cooking programme and talk to the camera as I go along. I'm 42.
There are more. Soooo many more.