Narrowing it down some more to not only 1) Stevie Lew mentions 2) on evening shows 3) in January-February, but also times 4) when April (presumably) wouldn't have been co-hosting at the time and 5) when Aaron was making eye contact with a proverbial "corner demon" a lot more than usual, I'm 99.99% sure it was the
January 31st STES starting at
timestamp 19:53 when something in the room got him so excited that he almost did a spittake, set down his beer and made a "hello what's this" face at something, followed with his eyes as though that attention-getter gradually walked toward the end of his desk, and then made a big thing out of aiming, zooming, and tapping his phone camera toward that end of the desk. If it had been any other time, that time sure would have been a lot less conspicuous than this: