During the Final Jeopardy segment, Agnes, the female contestant, starts with $3300, answers incorrectly, bets $2900 and thus is left with $400. When they later pan to a close-up of Agnes' podium, the amount shown is back to $3300.
Cliff Clavin's Final Jeopardy response appears, disappears and then reappears again throughout the round. It's most noticeable as Alex Trebek is explaining to Clavin that he'd surely win the game as long as he didn't do anything foolish.
When Timmy, posing as Sam, calls Rebecca for the "date" she is seen answering the call at Cheers. The number Sam would have for Rebecca in his stolen Black Book, would be her personal or home number, not her work number, which Sam would know already.