irregular verbs in english are weird

like, not even the fact that they exist, but rather how they interact with word formation

look at this list in wiktionary, there seems to be a general rule that if you add a prefix or another root to an irregular verb, it stays irregular -- "beget" and "forget" turn into "begot" and "forgot", "broadcast" remains "broadcast", and so on

and yet some of the more modern words don't work like that

"highlight" doesn't turn into "highlit", but "highlighted"
"screenshoot" doesn't turn into "screenshot" as a past tense verb, but "screenshooted"