Continuity mistake: The time gap between past and present seems to vary in different series, from 53 to 55 years.
Continuity mistake: When Phoebe kisses Gary, there's no lipstick mark on his cheek. But when he gets home, one has somehow appeared.
When Two Worlds Collide - S5-E3
Continuity mistake: Gary has to feel around in mid air for the portal as the wall has just been bombed. But when he reaches through, later, his arm comes out of the wall which has somehow returned.
