In the moments before her death on Star Trek: The Next Generation, Lt. Tasha Yar tells Capt. Jean-Luc Picard, “Death is that state in which one exists only in the memory of others … which is why it is not an end. No goodbyes. Just good memories.”

Since the Star Trek franchise was launched, it’s been home to actors who have bestowed good memories to fans.

The following is a look back at some of the late Star Trek stars we will miss forever. Some appeared in but a single episode of Star Trek television; others beamed into the franchise at multiple points, with a handful even playing multiple characters. All made lasting impressions.

The stars are presented in alphabetical order. The tributes to them are not meant as goodbyes. They’re meant to share good memories.

Star Trek: The Original Series
Star Trek: The Next Generation
Star Trek: Deep Space Nine
Star Trek: Voyager
Star Trek