Dilbert comes down to the caves where trolls (accountants) reside and gets a tour. The guide points to a troll sitting behind a desk, and mumbling in a stupor: "nine, nine, nine...".
Guide: And this is our random numbers generator.
Dilbert: Are you sure those are random?
Guide: That's the problem with randomness - you can never be sure.
Edit: Found it here: https://www.americanscientist.org/article/the-quest-for-rand....
And thank you, Scott - many laughs thanks to you.
Also the one where Wally insists his towel gets cleaner every time he uses it: https://br.omega.com/dilbert/311.html
There's one somewhere where they're eating lunch and I think Wally asks Dilbert if he has any extra napkins and Dilbert says he won't know until he's done eating.