Continuity mistake: When Bruce tears away from a clip a picture of Harvey, the clip was part of a clipboard with other papers underneath that, that are now gone. (00:06:00)
Continuity mistake: When Grace is crying over Harvey, she is holding a picture of him with her left hand while stroking the frame with her right hand. When the shot changes, she is suddenly gripping the frame with both hands. (00:06:15)
Continuity mistake: Grace puts down the coffee mug. When "Detective Leopold" shows her in close-up the beeper, the cup has turned around, with the handle where it would have been visible earlier (but it was not). (00:06:50)
Continuity mistake: The broken window pane on the door to the District Attorney's office changes slightly from shot to shot. When first shown, the break in the glass extends all the way up to the letter "L" in the word "law." When the shot changes, the break in the glass is nowhere near the letter "L." Also, the letter "W" in the word "law" is missing entirely, even though the break in the glass suggests a portion of the letter would still be intact if the letters were painted on the glass, as is standard. (00:10:25)
Continuity mistake: There's a marked cone of light on the door that leads to Harvey's room inside club Wild Deuce; it disappears after the opening shot. (00:15:05)
Continuity mistake: When the chandelier falls on top of Rupert Thorne, the tommy gun he was holding falls into the bright half of Two-Face's hideout. Later when Two-Face grabs the gun, it is in the dark half of the hideout. (00:19:15 - 00:20:10)
Continuity mistake: When we see Two-Face in full for the first time in the previous episode, his left eyebrow is white. In this episode, his left eyebrow is black.
Continuity mistake: When Harvey Dent is scarred in the previous episode, it's only the left side of his face and neck. In this episode and all others with Two-Face, his left hand is also scarred and discolored.
Continuity mistake: When Batman drives his two-wheeled vehicle out of the Batcave, there are no numbers on the concrete as they appeared in 1x8.
I've Got Batman in My Basement - S1-E20
Continuity mistake: The talon cuts on Batman's cape change in space and position between shots; they are firmly on top of the shoulders at the end of the struggle, but they were lower during the actual fight. (00:02:20)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Batman looks at the vulture after outwrestling it, and then, sprints to get his 'rang back. When he looks out he's got a cut on the suit, on the left, but when he fetches the weapon the torn part is gone. Cut away, and now the tear is back and doubled over to the other side. (00:02:55)
I've Got Batman in My Basement - S1-E20
Continuity mistake: From below, Sherman's red hair is visible, so he is on the left side of the sack of seed. In close-up though, he's in the middle, by the hole it leaks seed from. (00:05:15)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Batman and the kids approach the exit; you can see Roberta touching the push handle, but in the next, closer, shot they have yet to get there and Batman kicks the door open (without trying the panic bar). (00:07:25)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Mrs. Grant casts a shadow on the stairs that reaches a different point in different shots even if she did not move. (00:12:35)
I've Got Batman in My Basement - S1-E20
Continuity mistake: When the Penguin melts the front door lock, the holes on the door change distance between shots. (00:16:35)
I've Got Batman in My Basement - S1-E20
Continuity mistake: The balls of the bolas that tie Penguin up change position between shots. (00:18:00)
I've Got Batman in My Basement - S1-E20
Continuity mistake: When Mrs. Grant gets in the basement at the end, the Penguin is crushed under a long plank, different from the shelf that dropped on him earlier. (00:20:40)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Sherman hangs the two front pages overlapping in close-up, at distance in the next shot. (00:21:15)
I've Got Batman in My Basement - S1-E20
Continuity mistake: The size of the egg the Penguin's guys steal changes throughout the opening. It's twice as big as the ginger's hands when he holds it, but passed through a small triangular (for some reason) section they cut in the window, and when Batman reveals himself the egg is smaller.
Continuity mistake: The fat boss tells his underling that the prisoners will bring him "twice the gold ore." He asks then "Do you hear me?" The fan is in front of him or behind the back. (00:06:15)
Answer: She escaped off-screen and created a copy of herself to fool everyone.