The frequent co-stars were Andie and Ben again from their 2003 hit romcom.
The longtime co-stars had no problem poking fun at one another, and it all started when Hudson, 41, shared a clip from the film when her character, Andie Anderson, holds their "love fern" and storms off down the street past Benjamin Barry (McConaughey).
"Heard it was #TakeYourPlantForAWalkDay So, clearly I thought of one of my favorite co-stars... #TheLoveFern," she captioned the clip.
McConaughey commented on the post, writing, "Hate to see you leave, but love to watch you go. #ThatDamnFern."
This isn't the first time the co-stars have teased one another about their beloved film. Back in February, talk was once again on the fern when McConaughey posted a still image from the movie to his own Instagram, writing, "That damn fern."
Hudson reposted the photo, adding, "That damn fern...? That damn fern?!?! YOU LET IT DIE!"
The film centers around ad exec Ben, who bets he can get any woman to fall in love with him in 10 days at the same time as journalist Andie is searching for a man she can convince to break up with her in 10 days for an article.
For more from How to Lose a Guy, watch the rare footage below: