The Avengers actor, 51, leaped onto his own social media page to greet his Marvel brother-in-arms by posting the infamous picture of his costar wearing an "I Heart T.S." tank top.
Downey then captioned the embarrassing snap: “Join me in welcoming the biggest T. Stark fan of them all to Instagram! @twhiddleston.”
The fact his Iron Man character shares the same initials as the pop star clearly made the joke an easy one for him. Fans were quick to give Downey a pat on the back for his quip, but Hiddleston, 35, has yet to respond.
The British heartthrob kept his first post simple, choosing to upload a headshot of himself dressed as his supervillain character, Loki.
Alongside it he wrote: “He’s back!”
He is currently filming Thor: Ragnarok in Australia and spending time away from Swift, 26.
Hiddleston already has 533,000 followers since he joined Instagram, but that figure pales in comparison to his girlfriend’s 88.1 million.
Check back with Us Weekly to see if he makes a comical comeback at his cheeky famous friend.
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