Phelps, a last-minute addition to the event, gave his team a second-leg cushion that his fellow US swimmers didn't relinquish. In turn, he got himself a record 19th gold medal.
But that isn't the main reason the 31-year-old is hogging headlines as of late.
Prior to the 200-meter butterfly semifinals, the swimming legend was spotted shooting what could be the sharpest dagger look ever to his South African rival Chad Le Clos, who cost him the gold in the same event at the 2012 Summer Games in London. Phelps' Game Face: ON.
It was as if Phelps was ready to pounce on a prancing and—interestingly—shadowboxing Le Clos right in front of him. A death stare as intense as this was truly worthy of memes, and the Internet didn't disappoint.
For our part, we thought of real-life scenarios in which the seething anger in Phelps's epic staredown are most applicable. Indeed, if looks could kill...
1) Reading something "bad" about your favorite politician (or a teenager's favorable comment about Martial Law)
2) Catching your housemate gobble your last piece of cake in the ref
3) Getting blamed for your (younger) sibling's mess
4) Playing Pokémon GO while living in a rural area aka "the middle of nowhere"
6) Seeing your ex with somebody better-looking
7) Stuck in traffic...on a Sunday
8) Someone shamelessly cuts in line
9) Starbucks barista misspells your name
10) Cashier asks, "Sir, may smaller bill po?"