If something is 20% likely to happen, is it 100% after 5 times?

No. A 20% chance does not become 100% after five tries.

• Independent occurrences: Each attempt still has a 20% chance; an earlier outcome does not change the probability of the next one. 1
• Overall chance: Repeating attempts raises the chance of at least one success, but does not guarantee one. The episode’s “20 × 5 = 100%” framing is explicitly described as cumulative probability, not a certainty; it also distinguishes that from the chance on any single attempt. 2