From what we can gather, a song from the musical Hamilton was playing during her procedure which made her cry out of pure joy.
Sitting in the passenger seat of a auto, her speech slurred, Jen decides to phone a friend and recount - half-laughing, half-crying - how hearing a song from the Hamilton soundtrack while she was in the dentist's chair, moved her beyond belief.
We'll have some of what Jennifer Garner's having, please.
"Throwback Thursday- that time I had dental anesthesia...laughing gas + novocaine + Hamilton = you're welcome".
Miranda lovingly shared the video, saying Garner had shared it with him past year and he couldn't believe she posted it online.
In the video, the 45-year-old actress is seen sitting in the passenger seat of a vehicle talking about the "sad part" in Hamilton with someone over the phone.
Then she starts laughing and crying again - garbling her words through her heavily numbed mouth.
Garner's followers on Instagram were quick to applaud the star for sharing the moment. I said, it's so attractive.
Garner is speaking to someone (we're just going to assume it's her "Alias" co-star and Broadway legend Victor Garber) on the phone, but watch and judge for yourself below.
Completely enthralled, she continued, "Listen to the song. I told them about it, they have to see it".
"It was attractive - that music was so attractive".