The Blue Boy
The boy at the picnic was a hologram of Wesley Crusher. He was enjoying a picnic with his mother. He was ill-mannered and the mother chided him, saying that "Master Barclay" would spank him if he misbehaved.
Goddess of Empathy
The Goddess of Empathy was a representation of Deanna Troi, who Barclay had a crush on. In one scene he and the goddess had a romantic kiss. When Riker, Troi, and La Forge entered the program to find Barclay, they were greeted by the goddess, who was spewing romantic, soothing rhetoric. When asked where Barclay was, the hologram began to hit on all of them. (TNG: "Hollow Pursuits")
Musketeer Number One
Musketeer Number One was a holographic representation of Commander William T. Riker. He was a bumbling fool who was very short in stature, and stumbled up to the crew hunched over and screamed "en garde!" His voice was noticeably higher in pitch than the actual Riker's.
This hologram was designed by Barclay because Riker was very strict with him. The shortness of the hologram gave Barclay the opportunity to cut him down to size as Counselor Troi believed that he found Riker's height intimidating. (TNG: "Hollow Pursuits")
The Three Musketeers
While looking for Barclay, La Forge, Deanna Troi and William T. Riker came upon them. Musketeer Picard opined on the disagreeable nature of the real crew. The three challenged them to a fight. (TNG: "Hollow Pursuits")
Woman on a swing
The woman on a swing was a representation of Dr. Beverly Crusher. She was enjoying a picnic with her son and told La Forge that Barclay got into a bit of a scrap. La Forge found him fighting The Three Musketeers. (TNG: "Hollow Pursuits")