Townsend scored the equaliser for the Toffees against the Red Devils after 65 minutes and pulled out the superstar's famous 'siuuu' celebration.
The 29-year-old revealed mimicking the Portuguese had been planned the day before if he did get on the scoresheet, but had his heart in his mouth every time the ball went in the United box as the hosts searched for the winner.
Thankfully for Townsend, Ronaldo wasn't able to reply with a goal of his own, as the sides drew 1-1, and the Everton man explained it was done out of respect.
The winger joined Monday's talkSPORT Breakfast and revealed exactly what was going through his head.
Townsend said: "We were discussing it on the coach the day before on the way up to Manchester. The boys were saying, would you do it if you scored?
"I said yeah, but the one thing they said was make sure you are winning or it is late in the game, so Ronaldo doesn't have a chance to reply.
"I got a bit carried away, almost buckled and fell on my back, I looked up at the clock and it was 65 minutes. I gave the greatest player half an hour to make me look silly and score the winner. Thankfully he didn't.
"[I went] very early, every ball that went into the box I thought 'he was going to make me look a complete fool'. Thankfully we held out for the point in the end."
Townsend was able to get his hands on Ronaldo's shirt after the game, despite the Portugal superstar rushing off down the tunnel and appearing to ignore the Everton star.
Townsend added: "I made it my goal that I was not leaving Old Trafford without Cristiano Ronaldo's shirt. You saw after the final whistle, I ran straight to him, I don't know what he was muttering but it wasn't English.
"He was muttering in Portuguese and I asked him three or four times for his shirt and eventually he gave in and said he would give it to me inside.
"I had to wait inside the dressing room and thankfully the kit man was able to sort it for me.
"That shirt I am going to keep with me."