A remarkable number of voice actors for the show were starring actors in various Star Trek series:
Marina Sirtis (Deanna Troi on The Next Generation) - Demona, Margot Yale
Jonathan Frakes (William Riker on The Next Generation) - David Xanatos, Coyote
Kate Mulgrew (Kathryn Janeway on Voyager) - Queen Titania
Michael Dorn (Worf on The Next Generation and Deep Space Nine) - Coldstone
Brent Spiner (Data on The Next Generation) - Puck
LeVar Burton (Geordi La Forge on The Next Generation) - Anansi
Colm Meaney (Miles O'Brien on The Next Generation and Deep Space Nine) - Mr. Dugan
Avery Brooks (Benjamin Sisko on Deep Space Nine) - Nokkar
Nichelle Nichols (Uhura on Star Trek) - Diane Maza
Many also appeared as guests in Star Trek at one time or another:
Salli Richardson (Nidell in "Second Sight")
John Rhys-Davies (Leonardo da Vinci on Voyager)
Frank Welker (Voices of Spock screaming in Star Trek III, and the alien creature in "Nothing Human")
Clancy Brown (Zobral in "Desert Crossing")
Matt Frewer (Berlingoff Rasmussen in "A Matter of Time")
W. Morgan Sheppard (Ira Graves in "The Schizoid Man", Qatai in "Bliss", the Klingon warden in Star Trek VI: The Undiscovered Country, and a science minister in the 2009 Star Trek film)
Michael Bell (Zorn in "Encounter at Farpoint", Borum in "The Homecoming", and Drofo Awa in "The Maquis")
Gerrit Graham (Hunter in "Captive Pursuit", and Quinn in "Death Wish")
David Warner (Gorkon in Star Trek VI, St. John Talbot in Star Trek V: The Final Frontier, and Gul Madred in "Chain of Command")
Diedrich Bader (Tactical Officer in "The Emissary")
Clyde Kusatsu (Vice Admiral Nakamura on The Next Generation)
Paul Winfield (Clark Terrell in Star Trek II and Dathon in "Darmok")
Tony Jay (Minister Campio in "Cost of Living")
Patrick Stewart (Jean-Luc Picard on The Next Generation) was also considered for a role in the series, but his representation turned down the offer because his usual fees could not be met.
Creator Greg Weisman has commented that, at first, this phenomenon was unintentional. Marina Sirtis and Jonathan Frakes were both cast in prominent roles, and quickly the directors and producers began to think of other Star Trek actors when casting new roles.
This "Star Trek connection" was given a nod to by script writers in at least one instance within the cartoon. In the episode "Her Brother's Keeper" (1x12), Brooklyn remarks: "Yeah? You and what Starfleet?"