PB Pace stands for Personal Best Pace, a phrase used to indicate one is making good time and on pace to surpass their personal best completion time in a specific level or game. The phrase is also a nod to speedrunners and speedrun marathons such as Games Done Quick, a semiannual video game speedrun charity marathon.
The phrase was coined during Ian and Don Hit The Stream while they were checking out the Super Mario Maker 2 version 2.0 update that included a new online mode called Ninji Speedruns. In the mode, players compete for the best time on official Nintendo-made courses with new courses being added periodically. Both Ian and Don got caught up in trying to beat their best times, with Don in particular making great strides in the first Ninji Speedrun snow level.