All special moves can be done as a wake up attack. The number of invincible frames during the startup of a wake up attack is different from move to move. Some have none, some are semi invincible, some are fully invincible. The moves you see being stuffed during the first half of this video are semi invincible. Let's say Aquaman's Trident Rush has 20 frames of startup and 8 frames of invincibility. That means there's a 12 frame window where there's no invincibility. If you attack him during this window it will be stuffed. (Those are not the real numbers, I am just using them as an example). In this video you can see setups where Harley gets the knockdown and then these setups happen to be hitting him during that 12 frame window. However while these setups are good ways to time it anything can be used to hit them out of that 12 frame window if you time it right. So let's take Catwoman. Have her knock down Aquaman with 1,2,2. That's a hard knockdown that leaves him down for a while, giving you plenty of time to take a few steps forward and get the timing right. After taking a few steps do standing 3. If you time it right the standing 3 stuffs Trident Rush(and actually all of his other wakeup attacks as well). This is an easy example you can probably get it in a few tries. You can also do it with f+1,1,2 or b+1,2,d+3 or f+3 or whatever else you choose. There's a whole bunch of commonly used wake up attacks that people think are good that are only semi invincible and can be stuffed.