The Lucy Show - Season 1 Episode 26 -

Viv regrets letting Lucy talk her into joining her for a night-school chemistry class. Lucy gets carried away trying to invent a youth serum and develops a huge ego between explosions. To teach her a lesson, Viv and the professor make her drink her own concoction, which acts as a sedative. When she awakens, she's horrified by the results of her youth formula.