Riker wears the old-style com-badge, which suggests that he has been "abducted" from a time before 2370, i.e. before Voyager was launched and got lost in the Delta Quadrant. He should, therefore, have no knowledge of Janeway being captain of that vessel, as Janeway took command in 2371, but he does.
Janeway calls a Red Alert before heading to the transporter room to respond to B'Elanna's report that Q has beamed aboard, yet when Q transports the two of them to the mess hall, there is no Alert in progress. Q may have canceled it, yet the crew would have heard the initial warnings and begun moving to their designated areas. Instead, they are standing and sitting around like nothing has happened.
Commander Riker wears the old-style combadge and the old uniform, which suggests that he has been "abducted" from a time before 2370, i.e. before Voyager was launched and got lost in the Delta Quadrant; therefore, he should have no knowledge of Janeway being captain of that vessel. Janeway took command in 2371. While it has been stated that Tuvok and Janeway had served together before and that, prior to infiltrating the Maquis, he was Voyager's tactical officer, by the main events of Star Trek: Generations, Commander Riker was wearing both the new combadge and the new uniform by 2371.
Q2 is said to have been inside the comet for three centuries; yet, when B'elanna transports him aboard, he's wearing the current Starfleet uniform, which he should have had no knowledge of or been wearing.
There is no way that anyone could have observed the big bang from outside its origin (the singularity) because the entire universe itself was WITHIN the singularity.
Near the beginning, Captain Janeway uses Harry Kim's real name when giving him an order. She turns to Harry and says: "Garret........(and gives him the order)" - except Janeway calls Harry "Harry."
At 16:00, Q calls himself to the stand. It's obvious that his "counterpart" was filmed in different lighting, as seen on the hair color.
Q2's newspaper column (which can be read in freeze-frame) spells Continuum as "Conninuum."
Quinn serves Captain Janeway "Welsh Rabbit" like her grandfather made. The dish is actually called "Welsh Rarebit" and is made of toast and cheese, not rabbit. As a Q, he should have known this.