They suck very hard.
Pretty much anything with a mouse, or a high resolution display will crash if you touch anything. Normally they have around 3 chips, one big long one, one small long one, and a blob. You can't do anything with the blob, the long one will just crash, and the small one will mostly crash, but some points will "waffle" the speech. These normally have a resistor which can be skipped to make it pause on the current sound, but overall, that's the only thing you can do with them.
I just got a VTech PreComputer notebook II back from a really shitty car boot sale, and the only cool thing is a data "swap" where the sounds glitch a bit. Made around 1996. My old VTech PC Mouse was also just like this. I was a bit annoyed at the notebook one, so I spat on it, and now it doesn't turn on. I don't really care.
It seems everything pre-1995 is great. They glitch in some way everywhere, and there's always a nice crystal resonator thing there which you can touch to create some unique glitches, and you can change the pitch of them with a 555.