^^ Yeah! Most of the times he pops up when an opponent jumps at you with a flying kick/punch and you welcome him/her with an uppercut. At least for me, that is when he pops up mostly.
As for MKII, I don't remember him popping up in Scorpion fatality. On the screen it said TOASTY!! and you could hear it as well, but he didn't show himself. If I remember correctly in MKII, you had to press D,D,U,U,HP to get the toasty, if you only pressed U,U,HP you didn't get it.