After selling out New Yorks Beacon Theatre last weekend, Guster played an under the radar show at Bostons far more intimate Roxy Thursday night . The group and its current opening act, The Format, each performed a set of music at the small club before bringing their show to Bostons Opera House this weekend. Guster largely drew from its recent pair of albums, 2003s Keep it Together and 2006s Ganging up on the Sun, though the group did dip into its back catalogue and offered an odd cover of the 1930s dance number Brazil. Furthering its tradition of grand Boston entrances, Guster showed a mock ESPN video and carried the sports theme throughout its performances. At the start of the groups encore, the quartet brought Full House comedian Bon Saget onstage for a short skit that found the star running in through a huge banner bearing his name (according to the band, the stunt came as a surprise to Guster guitarist Adam Gardner, who wasnt clued in on the comedians cameo before he arrived onstage). Saget performed at the nearby Orpheum earlier in the evening and agreed to join the group onstage.