Visible crew/equipment: After Tara is found in the Janitor's closet and brought back to her room as Willow & Buffy come in, there is a mirror to the left of the door. It has a scarf draped over it to prevent it from reflecting things it shouldn't, but the bottom right corner is still exposed and in it you can see glimpses of the crew moving around behind the camera.
Where The Wild Things Are - S4-E18
Visible crew/equipment: While the house is becoming "Wild", Riley takes Graham down to The Initiative. Once the door closes behind them and the mirror returns to its original position, the shadow of a camera is reflected in the mirror. It's in the middle of the frame, on the left, over a book case.
Visible crew/equipment: In the episode 'This Year's Girl', when the Scoobies find the demon in the woods that Adam has cut open you can see a boom mike operator in the background. (00:07:40)
Visible crew/equipment: When Giles, Willow, Tara and Buffy (in Faith's body) arrive at the church in the armoured van, a camera is reflected in the van's back window.
Visible crew/equipment: The demons known as "The Gentlemen" always float about two inches off the ground. In one scene, two of them are moving through a park, and you can see the light blue cart they are standing on. (00:32:15)
Visible crew/equipment: In the last scene after Buffy jumps through the window into her mother's room, Faith and Buffy begin to fight. The two wrestle into the hall and begin to roll down the stairs. There is a side view shot then a front view shot. In the front view shot you can see a camera moving downward just outside the bannister and out of shot. Only visible in widescreen versions.
Visible crew/equipment: At the very end of the scene where Buffy and Giles discuss what happened (including The Initiative), you can see the microphone at the top of the screen. (00:39:45)
Where The Wild Things Are - S4-E18
Visible crew/equipment: After Anya has rescued Xander from drowning, they venture through the vines to the room that Buffy and Riley are in. The moment before Anya screams, "Xander, help me," a vine attacks her, but a crew member's hand can be seen (in the wide-screen version) moving the vine towards Anya.
The Freshman - S4-E1
Visible crew/equipment: When Buffy and Xander are doing some research, check the left side of the screen in a wide shot, when Xander asks "how far back do the disappearances go?" You may need to turn the brightness up, but there's a boom mike bobbing around. (00:34:25)
Where The Wild Things Are - S4-E18
Visible crew/equipment: When Xander and Anya pull over in the ice-cream van, the front windscreen is very reflective. To avoid reflecting the camera crew, a giant screen was put in front of the ice-cream van - which, ironically, is reflected in the windscreen. It isn't a reflection of another vehicle parked in front of them as the thing that is reflected is a curved shape.
Visible crew/equipment: When Buffy, Willow and Anya are watching Looney Tunes, some stage lights are reflected in the globe behind Willow.
Visible crew/equipment: During the scene of the siege at Giles', there is a shot where an Indian guy jumps through the window and helps himself by holding on to the sill. If you look to the left side of the screen, you can see it's a moving wall and that several hands of crew members are holding it so it doesn't shake.
Visible crew/equipment: In the scene where Willow visits Xander to discuss what may be going on with Oz; towards the end of the scene, when the camera is on Willow, you can see the sound mike at the top left of the screen next to the green crate in two different shots.
Visible crew/equipment: At the end when the gang leave the high school, stage lights are reflected in the broken glass of the double doors that they exit through.
Visible crew/equipment: When Buffy and Riley are talking at the crime scene, where he tells her about Maggie Walsh's death, one of the camera shots has a very visible black border around the entire edge of the screen as if the lens shade was visible in front of the lens and could be seen in the shot. (00:18:20 - 00:19:40)
Visible crew/equipment: In the scene where Spike escapes from The Initiative a black curtain can be seen to the right of the screen after the other vampire is release from his cell. The curtain serves no purpose to the set or scene and it disappears in the next shot. (00:13:25)
Where The Wild Things Are - S4-E18
Visible crew/equipment: In the scene where Xander and Anya make the last attempt to rescue Buffy and Riley, Anya is attacked by some vines and you can see another set of hands from the crew pushing the vine towards her.
Chosen answer: Angel is saying that he is still jealous and Buffy recognizes that this is his way of saying he wishes that they could be together. That is why they both smile.