Only funny if you're a Pratchett fan

The document I have spent much of today proof checking shows classic signs of too many people having an input, and one of these is an abrupt change of verb ending halfway through a sentence.

Thus it will say something like (totally made-up example to preserve confidentiality) "Jack is at the market buying a cow, picks up the groceries and haggles with magic bean vendors" when it should say "picking" and "haggling" to match the "buying". So I have crossed out the incorrect verb endings and written the correct ones in the margin.

In other words I have been busy writing "ing ... ing ... ing ..."