According to a former costar, a STD led to William Shatner becoming a star.

Christopher Plummer
was about to perform Shakespeare‘s Henry V in 1956 when he  paid the price for a steamy one night stand.

In new tell-all, In Spite of Myself, Plummer wrote that when he awoke after his romp, "I started to whimper like a whipped dog. 

"So this is what syphilis is like?"

As the pain intensified, Plummer’s horror mounted,

"It began to sink in…Shatner my understudy would have to go on! I screamed for a nurse who jabbed me with more morphine."

Shatner, filling in for the stricken star, seized the day.

"I knew then that the SOB would be a star," recalled Plummer.

It took Shatner a full decade to realize Plummer’s fear – with the premiere of Star Trek in 1966.