Full Idea
Adams and Leverrier began with Newton's theory of gravity, which made an incorrect prediction about the orbit of Uranus. They explained away the conflicting observations by postulating a new planet, Neptune.
Gist of Idea
The discoverers of Neptune didn't change their theory because of an anomaly
Source
Samir Okasha (Philosophy of Science: Very Short Intro (2nd ed) [2016], 1)
Book Reference
Okasha,Samir: 'Philosophy of Science: very short intro (2nd ed)' [OUP 2016], p.14
A Reaction
The falsificationists can say that the anomalous observation did not falsify the theory, because they didn't know quite what they were observing. It was not in fact an anomaly for Newtonian theory at all.