There's a long tradition of forced on-air breakups, particularly on smaller stations. An announcer, while reading a script, might suddenly find it on fire, torched by a smartass colleague.
Another common breakup method was for a "breaker" in the control room to walk slowly along the announce booth window, and with each step squat a little lower, giving the effect of him descending a flight of stairs. It was such a bizarre sight the announcer was sure to blow.
Another was for the breaker to kneel down close to the the window,
with his shoes perched on his shoulders, looking to the breakee like a very, very short person, with no torso or legs. Crossed eyes were optional.
Fortunately, most stations had a "cough button" near the announcer's mike, so, in instances of extreme breakup-ness, he could kill the mike until he regained his composure.