Plant ponies are sensitive to magic/timeline changes and stuff(if they're in the MLP universe as an oc)so they'd probably come out of hiding and enlist in forces against enemies, theyd be pretty useful cause tail They would know something isnt right/the same but it would only be an inkling not a full on "i know about timelines" thing, which would prompt them to do whatever they could to try and fix thats off even if they couldnt They'd have an inkling to whats the part that isnt right so yes fight the badguy cause he isnt suppose to exist a primal instinct would probably take over sending a signal saying "if thats gone then it gets better/goes back to normal"