Bruce covered the song only once:
1966-04-22 - MATAWAN-KEYPORT ROLLER DROME, MATAWAN, NJ
No other set details known. One show, a monster 'Battle of the Bands' orchestrated by promoter Norman Seldin, featuring 25 local groups. All the groups appeared at the same time in a large circle and performed three songs each. The winner was The Rogues (of Middletown), Second place was Sonny and the Starfires (featuring Vini Lopez on drums) and in third place were The Brew Masters. It was long thought that The Castiles placed third in this contest but in actuality, they did not place in the top five. The top three bands plus a selection of the other most popular acts were given an opportunity to perform at the Roller Drome the following week as part of a major concert headlined by The Dovells, The Ad-Libs and The Crystals. Springsteen, Vini Lopez and judge Vinnie Roslin (future Steel Mill bass guitarist) meet for the first time at this event. Lopez has recalled that The Castiles were the best band to play and should have won. In an interview on Little Steven's Underground Garage radio show, Bruce recalled that The Castiles performed Them's "Mystic Eyes" during a Battle Of The Bands event at the Matawan-Keyport Roller Drome in 1966. However, he also said that the prize for winning the Battle was to perform the following week with The Rascals, which does not tally with this event. It is possible that Bruce was mistaken, and perhaps was confusing this event with another - The Rascals did perform at the Roller Drome in early June 1966, but not as part of a Battle Of The Bands. Brucebase can find no information about another Battle at the Roller Drome in 1966 - certainly, none were advertised in the Matawan Journal. In that case, perhaps Bruce was mistaken about the prize, and it was this event he remembers.
Clinton Heylin wrote in his 2012 book E Street Shuffle: The Glory Days of Bruce Springsteen & the E Street Band that "Springsteen's initial singing duties in his first proper band, The Castiles, would be on a Them US A-side ('Mystic Eyes')." Heylin also quoted Tex Vinyard, The Castiles' manager, saying: "Soon, we let Bruce sing 'Mystic Eyes' and The Who's 'My Generation'. That's how we got the booking in New York." Vinyard was referring to the extensive series of about 30 shows The Castiles played at Café Wha? in New York City between late 1966 and early 1968.