Don't have a MIL, but I do have one by proxy - the OH's mum died when he was 12 and her twin sister has always kept a motherly eye upon him and his sibs.
She is lovely, but renowned for being a bit dappy and utterly tactless, everyone gets it from her so no-one is too offended, but here are a few of the things she's said to me:
"You must MAKE him stop smoking!" (yes, because I am Paul McKenna in disguise!)
On asking me if dd was talking in sentences yet, as her wunderkind gd1 was doing so at 9 months (yeah right) and being told no "well, dear, you do speak very fast, it's probably confusing her" (I'm from Liverpool and we do speak a bit quicker up there, but wtf?? How does she think babies learn to speak on Merseyside?)
When I vaguely floated the idea of going back to the clinic to talk about having a sib for dd - "Well, I told DIL that she's far too old for another, so you definitely shouldn't be thinking of it" - DIL is 35 and I was 39 at the time...
But then she used to moan to me about her student ds2 and her fears that he was gay because he hadn't brought anyone home to meet her - at the time her ds2 was sh@gging my sister (I only knew because sister had confided in me) so I had to go 'oh, really, do you think? No, I'm sure he'll meet a nice girl soon...' while trying not to explode laughing...