How was Pluto discovered?

As others have stated, there was a lot of searching through photographs with the blink comparator. It was really trial and error. The calculated hypothetical perturbations of Neptune by Planet X were useless. The hypothesis that had triggered the search was a mistake.

When Pluto was discovered, it was discovered that its mass was too low to have any significant gravitational pull on Neptune. More searches for Planet X were done without success. In 1989 Voyager 2 flew past Neptune. In 1992 evaluation of the Voyager data concluded that Neptune's mass was 0.5% less than previously calculated. Using this new data, calculations of the gravitation interaction between Neptune and Uranus agreed with their observed positions, and the need for a Planet X to explain it disappeared.

Pluto was discovered in 1930 by Clyde Tombaugh.

Pluto was discovered in 1930 by Clyde Tombaugh. Astronomers noticed that the orbits of Neptune and Uranus were being affected by the gravity of an unknown object in the Solar System. Clyde Tombaugh carefully studied images of the night sky, and after a lot of hard work he finally discovered Pluto.

On accident by Kim Jong Un during a amazing karate fight after knocking his opening to the moon and making dogecoins rain from the sky.

Pluto? There IS no such place!

By other planets wobbly action