John Lennon saw more than Lucy In The Sky with Diamonds in 1974.  He was apparently given a small egg shaped metallic-looking object which he in turn gave to Uri Geller, the psychic.

He didn’t know what the purpose of it was, but he claimed he had been given it by an extraterrestrial.

In 1974, he also spied a UFO from the window of the penthouse he shared with then-girlfriend May Pang.

”He was with his assistant, Mary Pang, when he walked out on to the balcony and spotted the UFO.

"It looked like a flattened cone with a brilliant light on top" Mary Pang said.

Source: http://www.thesun.co.uk/sol/homepage/features/2655271/Celebrity-alien-encounters.html?offset=8#ixzz0UCSlSwEe