In the Trophy Room on the level "Imperial Kashykk", you can find the monsters that Obi Wan, Anakin, and Padme fought in the arena in Episode 2 as well as Jar Jar Binks in frozen carbonite.
The Apprentice's nickname is "Starkiller". This name originates from early drafts of the first film, where the protagonist was named Annikin Starkiller.