Lindsay Lohan just got nasty on Ariana Grande's Instagram selfies.

I have no shame in admitting that one of my favourite pastimes — when I’m not, you know, reading about important things happening in the world — is watching celebs interact with each other on social media.

(Yes, I know, I really should think of something better with my time…)

via GIPHY

It’s mostly all fun and games, but sometimes… well, sometimes things get a little interesting.

Over the weekend, Lindsay Lohan decided she would take a scroll through singer Ariana Grande’s Instagram profile and mercilessly troll her in the comments section.

Yes, it was very Mean Girls and no, no-one has any idea why she did it.

via GIPHY

So far, Lindsay’s comments have been spotted on three of Ariana’s snaps, and they all say, “too much makeup”, with no other explanation.

#lindsaylohan went on three #arianagrande posts and commented: #toomuchmakeup ????????

A photo posted by The Archive of Shade (@theartofshade_) on Nov 19, 2016 at 12:37pm PST

Ariana’s fans – of which there are 89.3 million of on Instagram – weren’t taking Lindsay’s bizarre comments lying down, and they soon took aim at The Parent Trap star on her own social media account.

On the 30-year-old’s Instagram account, Ariana’s fans have flooded the comment section with sentiments like, “too much jealousy” and “too much drugs”.

They've also offered messages of support to the 23-year-old singer, defending her against the negative comments.

"Your makeup is on fleek...keep slaying and ignore the haters," read one comment, while another fan wrote, "Don't worry about what others say behind your back."

While I don't know what Lindsay plans on commenting next, there's one thing I definitely know for sure: trolling the comments of your fellow celeb's Instagram is most definitely a very un-'fetch' thing to do.

Sam Frost talks tackling her Instagram trolls with Mia Freedman on No Filter: