in stargate, one of the only slightly better than average scientists (who were outclassed by david spader) was the women who played george castanza's contact at the unemployment office on seinfeld.
planet of the apes was completely saturated with bit players from twilight zone, star trek and lost in space. two of my favorites were the second fbi interrogater who also played the jealous lover on star trek's "wink of an eye" (he was also the evil scientist in "the head that wouldn't die")
also one of the reporters who got right into the chief security advisor's face was the same actor who portr
ayed the captain of the ill fated outpost 5 on star trek's "balance of terror". he was on screen for 10 seconds and then switched his camera onto a romulan ship just as they fired and blew him up.
more later.