It all started with a brief video in which Mendes is seen in a fun and flirty purple patterned dress that she called her "favourite", reports eonline.com.
"I think I resemble a horse at times. It's not a bad thing. It just is. If I was an animal I'd clearly be a horse. Or a Shetland pony," she captioned her video, which also showed her smiling from ear-to-ear.
"Anyway here I am horsing around in my new favourite dress. I LOVE THIS DRESS!!! Thank you @alejandroblanco for creating this with me! Love love love this," she added.
However, not everyone was a fan of the design.
"Don't like these designs you need a better Designer you to pretty for these ugly patterns," one person wrote underneath the actress' post.
However, it was Mendes' response that got even more people talking in the comment section.
"I'm so sorry you don't like this one. It happens to be my favourite piece of my new collection," she responded.
"But I'm sure there's other stuff you may like. If not (Kate Hudson) and (Gabrielle Union) design some great things. So there may be something for you there."
The actress added: "Sending love for 2020."
( With inputs from IANS )