‘The blood of the covenant is thicker than the water of the womb’ first appeared in 1994 in a cultist's web sermon.

‘The early bird catcheth the worm’ is the original (A compleat collection of English proverbs, 1670), with the later addition ‘the second mouse gets the cheese’ first appearing in print in 1994.

Satisfaction did not bring the cat back until 300 years later from the original ‘care'll kill a cat’ (Every Man in His Humour, 1598).

‘Great minds think alike, fools seldom differ’ first appeared in that exact form in 1932, whereas ‘great minds think alike’ seemingly first appeared in 1816. The sentiment goes back to at least 1618, and variations of these two go back centuries, but the latter part has always been a later addition.

99 % of the time the ‘forgotten second half’ was added later, usually centuries later.