I came here just to add to the quiet rather than poor for the mouse. Also, most of these are just repeats from the first. So I suggest the inclusion, "lazy as the OP" :)
I've heard both quiet and poor for church mouse. Google as of today has 66k of "quiet as a church mouse" and 47k of "poor as a church mouse". Not that it's my quiz but I think either one should be acceptable.
Why would a church mouse be poor with all the communion matzoh and wine to consume? - Drunk as a Church mouse would be more apropos. (Though I've only heard of "Quiet as a Church mouse").
http://clichesite.com/content.asp?which=tip+1065
The mouse is so quiet that you can't hear it even as it scurries over the floor of a church, where everyone is silent in prayer.
I believe the paradigm that church mice are both poor AND quiet is well-established in Disney's (animated) Robin Hood film.
Quiz creator, fix this. Please.
The original (and complete) phrase was "happy as a clam at high tide".
Due to the obviously exhausting nature of saying that entire phrase, over the years, it has gotten truncated down to simply "happy as a clam".
then got it with poor. No biggie. Great quiz.