Does a 2000 Toyota Echo have to have iridium spark plugs?

No, but its the best you can get in the market. Faster starts, prevents cold start wear in the winter, better throttle response, and fuel economy. The original equipment spark plugs for the 2000 Toyota echo were indeed iridium, and they do not need to be changed for 100,000+ miles. I definitely recommend using iridium plugs when you must replace the OEM plugs. You should be able to check with the maintenance manual that came with your car for more info. But no cars REQUIRE iridium plugs. In fact, none of the Toyota Echos after 2000 came with those amazing iridium plugs that the 2000 model had from the factory. Also note that you may not even be able to buy those plugs at all anymore, from what I understand they had a special extra wide gap. The replacement plugs may have a smaller gap, and even if iridium, they may not be intended to last for 100,000+ miles. Most Echo owners consider the Denso (Part #SK16R11) or NGK (Part #IFR5T11) Iridium plugs to be the best replacement for this vehicle and they can both last for 100,000+ miles like the original equipment plugs.