Riddle 1: What's the probability that a Bernoulli distribution's variance is always positive?

Answer: It's not, actually. It's always non-negative.

But don't just take our word for it, check the math for yourself.

Riddle 2: How many Bernoulli trials do you need to flip a fair coin to get 100 heads? Conditional Probability Fest: Bernoulli's Riddles

Riddle 3: What's the probability of a Bernoulli process having a negative probability mass function?

Answer: You can't, actually. It's always non-negative.

But don't just take our word for it, check the math for yourself.