You should watch:

The Mind's Eye

This was episode number 24 of season 4.

The following characters appeared in this episode:

(as Larry Dobkin)Ambassador Kell
(uncredited) Ensign Kellogg
(voice) Enterprise Computer
(voice) (uncredited) Sela
Captain Jean-Luc Picard
Chief Miles O'Brien
Counselor Deanna Troi
Commander Wiliam T Riker
Doctor Beverly Crusher
Governor Vagh
Lieutenant Worf
Lt Commander Data
Lt Commander Geordi La Forge
Taibak