Continuity mistake: After Karen takes the red bag off of Grace's head when they enter the arcade for her birthday suprise, the position of Grace's hair differs in the next closeup.
Continuity mistake: When Grace and Leo accidentally meet each other in their apartment, ruining Will's surprise, they have a cuddle, then Leo walks over to the fridge. Between shots the back of his collar changes from folded down to folded up.
Continuity mistake: When Karen and Jack are eating outside Jack's apartment on the small table, they both have plates of egg. Between shots during their conversation, the arrangement of the egg on their plates changes a few times.
Continuity mistake: When Will gets up from the sofa, as he speaks with Grace, a small white cushion with black dots all over it falls over on the sofa. In a following shot you can see that the cushion has now magically up righted itself.
Continuity mistake: After Will puts on his robe because Leo walks in, Will ties the robe straps so that one strap is much longer than the other one. During his conversation with Leo though, between shots, the straps suddenly both become the same length.
