I just finished playing Mr. Do! and I scored a diamond on subsequent levels (6 & 7) ... never won "2" specials in one game before.

So it makes me wonder, if I can ask the propeller-heads that can read its machine code, what are the odds of a diamond appearing?

You could try asking Don Hodges, if he's in the mood.
http://www.donhodges.com

I mean, he's on fire lately.

Awesome reference to a cool site, thanks!

http://www.donhodges.com/mr_do!_diamond_trigger.htm

easy setting: overall 1/512 chance to get diamond
hard setting: overall 1/2048 chance to get diamond

Aaaah, I can sleep at nights now ... 8)