Originally recorded by Limmie Snell aka Lemme B. Good (1965).
Hit versions by The Olympics (US #81 1965), The Young Rascals (US #1 1966).
From the wiki: “The song was first recorded in early 1965 by Canton, Ohio, R&B singer Limmie Snell under the name ‘Lemme B. Good’. About a month later the song was covered — with considerably rewritten lyrics — by R&B/novelty artists the Olympics, but this version was only moderately successful at best, reaching #81 on the Billboard Pop Singles chart.
“The tale is told that Rascal Felix Cavaliere heard the Olympics’ recording played on a New York City radio station and the group added it to their concert repertoire. Co-producer Tom Dowd captured this live feel on the recording, even though the group did not think their performance held together well.