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The example with Bernice could be the "personality inversion" portion of In Vino Veritas.
Gaining a physical ability might count as Drunken Master. Although it may not normally include walking, obviously that's a struggle for anyone with a physical disability so the alcohol in Jewell's example would be a major physical coordination boost, like if someone chugged a few shots of spirits and then won a gold medal in gymnastics.
Is there a trope for when someone’s behavior becomes less whacky, rather than more, when they are intoxicated? Bernice from Designing Women was a Cloud Cuckoolander who became intelligent, sane, and rational when drunk. Comedian Geri Jewell, who has cerebral palsy, jokes that when she’s drunk she walks perfectly straight. And I just got a laugh out of my daughter by saying that when a Furby gets drunk, it speaks plain English. What trope is in play here?