Actually, depending on your definitions, there are eight, ten, twenty-one, eighty thousand, or several million planets in the solar system. Ceres was considered a planet (The tenth one) until the 1850s. 2003 UB313 is actually larger than Pluto is, too.

America was named after a Welsh (ew) businessman named Richard Ameryk, not after Amerigo Vespucci (Were it the latter, it would be called something like Vespuccia, because places get named after the discoverer's surname).

Cockroaches aren't actually that great at living through a nuclear war. Whilst doing better than Humans, they're one of the least rad-resistent insects around. A fruit fly dies at around 64,000 rads, whilst a cockroach at only 20,000 (Humans are about 1,000).

Oh, and lemmings don't commit mass suicide. They merely panic.