This was written by Bob Welch, who was a guitarist and vocalist in Fleetwood Mac from 1971-1974. Welch, who died in 2012 at age 65, gave us the story behind the song. Welch wrote: "'Hypnotized' was first a 'shuffle-time blues rocker' for singer Dave Walker (ex-Savoy Brown lead singer) when Fleetwood Mac had Dave on board as a band member for a (very) short while. When we realized that Dave was not fitting in musically with what we were trying to do, I hurriedly re-wrote the lyrics in Christine McVie's upstairs living room at 'Benifolds,' the 'mansion' south of London where we all lived and recorded at the time - it was a 20 room house. The 'playing field' mentioned in one of the verses made a reference to the large grass tennis court which was part of the property... and kind of spooky at night.
I was (and still am) interested in the paranormal - UFO's, the Carlos Castaneda books about the Yaqui Indian 'sorcerer' Don Juan - so I incorporated a lot of these themes and references into the song. The 'place down in Mexico' refers to Castaneda's Yaqui sorcerer, Don Juan, who is presumably doing 'astral' travel ;-). The 'strange, strange pond' with 'sides like glass' refers to a strange anomalous depression in the North Carolina woods near Winston-Salem, North Carolina which a friend told me about, which, at the time, freaked him (and his dirt-biking buddies) out."