Although Nicky Hopkins played piano on two tracks of "Between The Buttons", he and Ian Stewart obviously hadn't met yet. Most probably Hopkins' parts were recorded during mixing and overdubbing sessions in January 1967, which Stu didn't attend. According to author Len Comaratta "in the spring of 1967, guitarist Jimmy Page invited Nicky Hopkins to record on some songs for the Yardbirds' "Little Games" album. During these sessions, Hopkins made his impression on the Rolling Stones' founding member and pianist, Ian Stewart".
Both Stu, who already knew Jimmy for a long time, and Nicky perform on the final album. Hopkins contributed to the tracks 'I Remember The Night', 'Stealing, Stealing', and "Smile On Me", while Stu lended his boogie piano to "Drinking Muddy Water". When we take in mind Stu's disliking of what was going on at Olympic Sound Studios, he must have felt comfortable during the "Little Games" sessions. Session player Nicky Hopkins had of course another stake, and afterwards joined the Stones to record "There Satanic Majesties Request", eventually performing on all album tracks.
Adapted from the following source: Len Comaratta, Icons Of Rock, Hot, 2010.