Revealing mistake: When Station 51 is dispatched to 'man trapped', just as Engine 51 rolls out of the apparatus bay and heads down the driveway, the real 127's vehicle is seen parked inside the bay, near the rear door.
The Girl on the Balance Beam - S5-E18
Visible crew/equipment: While en route to the woman trapped on a wire, the reflection of the cameraman is visible on the windshield after Mike drives past the entrance to Commercial Studios. We see it's not Captain Stanley, but instead it's someone wearing a white shirt, holding up something (presumably the camera) with both hands.
The Girl on the Balance Beam - S5-E18
Visible crew/equipment: At the gym, when Nancy wants to prove that she's feeling fine, she tries to do a cartwheel, and the outlines of the mic transmitter and wire are visible on the back of her leotard.
Continuity mistake: When Station 51 is dispatched to a structure fire (with the two girls trapped upstairs) the address given is 1911 Harper Ave, but when they reach the house with the fire, directly across the street that house number is 1637.
Continuity mistake: When Johnny's on the phone with Uncle Ernie about the new color TV, in the wide shot Johnny writes down the address of the warehouse, and puts the pen back in his shirt pocket. Then Johnny thanks Uncle Ernie, and when he hangs up the phone, in the next closeup the pen is back in Johnny's hand.
The Lighter-Than-Air Man - S5-E8
Continuity mistake: At the scene of the overturned truck causing toxic smoke, when Chet talks to the driver and then pops out the windshield, in the wide shots the two windshields are intact and not cracked, but in the closeups facing Chet and the closeups facing the driver there are long cracks in the windshield.
Visible crew/equipment: When the man who was unconscious for five minutes is wheeled into the ER, Morton has him taken to treatment 2, and when Carol is taking his blood pressure, the actor's tape mark is visible at her feet, under the gurney.
Continuity mistake: When Station 51 is dispatched to the landslide, the address is given as 2283 Canyon Road, but when they arrive at the house the address is 4102.
Visible crew/equipment: At the construction site with the cardiac arrest, the outline of the lavalier mic transmitter is visible on the back, left side of Johnny's shirt, particularly when lifting the man onto the ambulance stretcher.
The Lighter-Than-Air Man - S5-E8
Visible crew/equipment: At the scene of the bride and groom's traffic accident, when Johnny asks Crockett if he ever thought about a career as a marriage counselor, the outline of the lav mic transmitter is visible on the front of Johnny's shirt.
Visible crew/equipment: After Chet falls through the roof at the structure fire, when Truck 3 raises their ladder, we can see the cameraman/camera's shadow just as the ladder reaches the roof.
Pressure 165 - S5-E7
Visible crew/equipment: When Station 51 is dispatched to the structure fire at the flour company, while en route there's a closeup of Squad 51, and the reflection of the filming vehicle can be seen in the spotlight.
Continuity mistake: When Dixie is having a heart to heart talk with Karen, in the shot facing Dixie she reaches out with her left hand to take the napkin from Karen, but in the closeup it's her right hand that takes the napkin. Additionally, the napkin she takes from Karen is perfectly folded, but it was wrinkled and messy when Karen held it.
Continuity mistake: When Karen first walks into Station 51, her handbag is over her right shoulder, then over her left shoulder and back to her right shoulder again.
Continuity mistake: At the scene of the vehicle accident, when the boy is removed from the overturned car, he has a bruise near his chin that reaches below his mouth area. When he's in the ER, that bruise is now twice the size and reaches his cheek area.
Continuity mistake: When Roy and Johnny climb the electrical tower to rescue the sky diver, in the closeups Johnny hangs onto the diagonal cross beam when he reaches out to Lucky, but in the wide shot the stunt double hangs onto the tower's main vertical frame when he reaches out to Lucky.
Continuity mistake: It's Squad 39 at the construction site with the cardiac victim, but en route to Rampart we see Squad 51 following the ambulance.
Continuity mistake: After examining Tommy, when Brackett speaks to Mrs. Lawson, the boy's mother, her handbag is hanging off her shoulder in all the shots facing Brackett, but in all the shots facing Mrs. Lawson the bag is gone.
Deliberate mistake: When Johnny and Roy are on the Coast Guard copter, responding to 'victim down at cliffs at Catalina Island', there are four closeups of the guys looking out the windows which are flipped shots - note their uniforms are backwards, the paramedic patches are on their right sleeves instead of their left.
Visible crew/equipment: When the man, who walked in with his daughter, has a heart attack at Station 51, while he's lying on the floor in the apparatus bay we can see the top of the set, the part of the ceiling that's incomplete.
Answer: I believe you are speaking of the old man, Mr. Wilson. He's played by J. Pat O'Malley.
Bishop73
Correct, it was J. Pat O'Malley...he also played the grandfather with his grandson when their rocket exploded, and also played "Old Bill" in the episode with Ann Prentiss, where Gage saves the little girl from the burning tree house, and her mother falls in love with him.