The Rika clone is named Kuyoh. She's an alien like Yuki but is from a different faction.
The one with the ice cream is Sasaki and it the total opposite of Haruhi by being cold and emotionless.
The pigtails girl is Kyouko and she's an esper that got her power from Sasaki instead of Haruhi. She's as lesbian for Sasaki as Itsuki is for Kyon.
The guy in the background calls himself Fujiwara. He's a time traveler and he's a prick.