There is precedent in DKC3, where Dixie Kong and Kiddy Kong turn into Ellie the Elephant to drink a weird waterfall creature named Squirt and then shoot his squirt water back in his eyeballs, blinding him until he spits out a jet ski.
I'm not saying it's a GOOD idea, but there IS a reason to assume that if a Kong transforms into an elephant, they can identify someone made out of liquid can be sucked and spat back out. Mostly because a literal toddler has done it before.
Mario Vs Cloud 2002: A Video Retrospective - https://youtu.be/1dx4t6H_K9Y
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