Who played piano on the Bobby Darin hit single "Dream Lover"?

I believe it was Neil Sedaka

Neil Sedaka - it was indeed he. Fine answer!

* Date: Thursday, March 5, 1959
* Location: Atlantic Studio, New York City
* Songs recorded: Dream Lover (Darin), Bullmoose (Darin)
* Producer: Ahmet Ertegun and Jerry Wexler
* Engineer: Tom Dowd
* Personnel: Bobby Darin, vocals; Neil Sedaka, piano; other details unknown

The arrangement of "Dream Lover" was more sophisticated than on his previous records and this, allied to more elaborate production, accounted for the 32 takes it allegedly took to complete the recording. For this particular session, Bobby was happy to have someone else take care of the piano playing so that he could concentrate on singing. The pianist in question was none other than Neil Sedaka, who had only scored one hit until then, "The Diary" (still at #47 in that particular week), but his second RCA single, "I Go Ape" was about to enter the Hot 100, in mid-March. On "Dream Lover", Sedaka's piano is barely audible, but he surely makes his presence felt on "Bullmoose".

http://www.bobbydarin.net/sn_030559.html