2. How Long Is Forever? (2.1)
How Long Is Forever? is quite possibly the most bittersweet episode in the entire series and easily the best to feature Starfire as the main protagonist. Following the former Tamaranian princess witnessing a quarrel between her friends and a fight against a time-traveling villain going terribly awry, she finds herself trapped twenty years in the future.
She quickly discovers that Cyborg is now an obsolete hunk of machinery who can no longer leave the abandoned Titans Tower, Beast Boy has been relegated to the life of a circus freak, Raven has become a mentally unstable recluse, and Robin has become Nightwing (a very cynical version of Nightwing, mind you.)
This episode is essentially Starfire living out her worst nightmare and the stages of her coming to terms with this new reality is incredibly harrowing. The final, semi-triumphant act does act as something of a remedy to the dark episode, but without taking away from the severity of it all. On the contrary, it plays to the episode's theme of writing one's own destiny incredibly well and the whole thing acts as a cautionary tale as to what can happen when anger wins out over friendship.