Turns out, Tom Hiddleston IS a big T. Stark fan, after all!
The Avengers actor proved he can take a little teasing on Wednesday while addressing his co-star Robert Downey Jr. welcoming him to Instagram this week by poking fun at that 'I Heart T.S.' shirt he wore at the start of his his whirlwind romance with Taylor Swift.
"Join me in welcoming the biggest T. Stark fan of them all to Instagram!," Downey Jr. wrote, referencing his Avengers character, Tony Stark aka Iron Man, who bares the same initials as Hiddleston's pop superstar bae.
MORE: Robert Downey Jr. Welcomes Tom Hiddleston to Instagram With a Little Friendly Shade
"We're very close," Hiddleston said during a Facebook Live Chat with the Los Angeles Times. "There's a lot of mutual affection."
The 35-year-old actor shared that he and 51-year-old Downey Jr. bonded while working together on The Avengers, and have a lot of "mutual admiration" for one another.
MORE: 13 Reasons Taylor Swift and Tom Hiddleston Are Absolutely Perfect for Each Other
"It's great, he's very sweet," Hiddleston added with regard to the lighthearted dig.
Meanwhile, Downey Jr. echoed this sentiment on Wednesday, when he followed up his initial Instagram with a pic of Tony Stark showing off his affection for Hiddleston's Marvel character with an "I Heart Loki" tank top.
WATCH: Inside Taylor Swift and Tom Hiddleston's Latest Date Night -- Smiles, Stolen Kisses and Security Guards!
There's just so much superhero BFFing going on right now!
Watch the video below for more on Hiddleston's Instagram debut.