Farming is very easy mode, and it shows. Its industrious sister, mining, is choc full of danger despite being of the same reward and engagement level. It shows the handholdy, casual nature of this PvP game that enables casuals to accumulate unreasonable amounts of carrots at no cost to themselves.
Since mining has to be pointlessly obnoxious and full of interruptions, and we can't just copy the creatures from mining, I say we reskin them.
First and foremost, since water grows crops, and slimes are 99% water, and crops are alive, we could certainly have brown mud slimes, born of the raw life of the field. Way more believable than a wet globule suspended within pure dry rock. Depending on the quality of the crops farmed, these slimes would get much stronger.
As for a parallel to boreworms, we of course need giant, rabid moles. Once in a blue moon, we could even pull up crops that lead to mole dens. Two birds with one stone, fucks up the farm, the farmer, AND creates engaging content. These moles would flee and reburrow and be just as obnoxious as the normal moles and boreworms, in a double whammy.
Both of these frightening creatures could come with a horrible suite that take 50 mental weight for no particular reason at all and aren't even worth 5 mental weight, as well as craftables, and whatever else comes with dungeons, for the mole.
People are free to add on ideas, but for too long farmers have had to do this content that takes as long as a full time job with no hindrances or tedium, besides the fact it takes forever.