Don't Date My Sister!

Joannie Cunningham takes a ride with Fonzie's mini-me, the Bosom Buddies come to blows, and Alex P. Keaton is up all night worried sick, young lady... We're back for YEAR TWO of The Sitcom Study and this week's trope is Don't Date My Sister! Here's what we're watching:

• Happy Days S2 E8 "Not With My Sister You Don't"
• Bosom Buddies S2 E17 "Not With My Sister You Pig"
• Family Ties S1 E2 "Not With My Sister You Don't"
• Herman's Head S1 E25 "Twisted Sister"