For nearly six decades, Star Trek has built one of television and film's most expansive shared universes. But unlike comic book crossovers that sometimes feel reverse-engineered to tie things together, Trek's connective tissue-from The Original Series to The Next Generation and beyond-has usually grown organically. A familiar character steps through a turbolift, an old starship is spotted or a legacy figure returns to bridge the gap between generations. These crossovers are part of what gives Star Trek its lived-in feeling: no crew exists in isolation and the galaxy always remembers its past.