Minnesota Department of Natural Resources, "females lay up to 20,000 eggs which normally hatch within one week. Large schools of tiny, black tadpoles feed together along the edge of shallow wetlands, emerging as a mass of tiny toads within approximately six weeks. Maturity occurs in two to three years."
The general consensus on the Internet is that kissing toads will not give you warts (although touching toads may cause skin irritation, especially around the eyes or in the mouth). Kissing (or more general contact with) princesses (or princes) may, on the other hand, pass wart-causing viruses between people.