Visible crew/equipment: (Ep. 2) When The Doctor, Jo, and Dr. Tyler are taken into Omega's palace, in the first shot of the multiple passageways (right before Jo says that it looks like Aladdin's cave) the curved chalk actor's mark is visible on the floor, then we see it again in three following shots. Note that when they're all escorted further inside, just as Dr. Tyler comments about the matter/anti-matter not making sense, Jon Pertwee looks down, presumably to make sure he hits his mark.
Visible crew/equipment: As the energy being moves down the city sidewalk, we see its shadow on the concrete. Right beside that, however, we can also see the distinctly-shaped shadow of the camera. (00:35:00)
Angels Travel on Lonely Roads (2) - S1-E22
Visible crew/equipment: After Kimble finishes stacking wood in the barn and is putting his shirt back on, the boom shadow moves across the wooden chair hanging on the wall behind him. (00:25:00)
Who Killed Avery Lord? - S1-E23
Visible crew/equipment: After the woman in the negligeé goes back into her apartment, a crew member's shadow appears on the corridor wall. (00:42:00)
Visible crew/equipment: In the 1987 Mt Rushmore conclusion, when Robert knocks Duke out with the infamous WSB chop, the put Duke on the couch. When Sean is tying Duke up is apologizing to him, at the end of the couch for several seconds (behind Duke's head) you can see the camera man moving.
When You Get Back to Mars, Are You Going to Get It - S3-E24
Visible crew/equipment: When Tim and Martin are carrying Andromeda to the bedroom and Martin opens the door with his Martian finger, the crewmember actually opening the door can be seen on the hinged side of the door. The crewmember continues to move in that space for about 3 seconds during the scene. (00:10:00)
Visible crew/equipment: After Graig returns Patty's math book, Cathy tries to use the pamphlet's rules as she follows Craig. When Craig thanks Cathy for helping him with Latin, the boom mic repeatedly pops up into view in the bottom right corner of the screen. (00:18:10)
Visible crew/equipment: While Uncle Joe is outside Drucker's store, when the two women approach him, there are two T-marks on the ground where they stand. (00:03:10)