SAY What?

My Spanish is good. I'm sort of half way between C1 and C2 level. I'm proficient enough that I can work as a translator but not fluent enough that people confuse me for actually being Spanish. But I'm working hard on that. And I thought I was getting good at it. Until this happened.

I do Capoeira in gym about a 10 minutes cycle from my house. It's usually a pretty pleasant cycle but this day I hadn't noticed the gale force winds as I left the house. By the time I arrived, the sweat was pouring off me, my legs were jellified and my heart was racing. I was gulping down water like there was no tomorrow.

Within a minute of arriving the instructor said:

"Bueno chicos, a calentar" (Right guys, let's warm up)

My response? My head said "I'm already warmed up". My mouth said "ya estoy muy caliente" (I'm already really horny)

This wouldn't be so bad if last week, when we were told to run laps around the sports hall, I hadn't complained and told everyone "odio correrme". Correr means 'to run'. Corrrerse means to orgasm. 

As you can imagine... I'm starting to get a bit of a reputation at the gym... 

What mistakes have you guys made in Spanish?