Natsu takes advantage of the situation

While Natsu was mortified at being in Wendy's body, he quickly realized he could have some fun with it. If Carla believed he was Wendy, then he could easily masquerade as her for the time being However, he did want to get back in his body, so he resolved to stay as Wendy until he found his body. After a period of silence, Natsu/Wendy replied "Yes Carla I'm fine."

"That's a relief Wendy. I was worried something was wrong with you. Now,move your cute butt Wendy, we're on a mission." Carla said.

"Okay Carla." Natsu/Wendy replied.

"I hope you remembered to relieve yourself Wendy. The train ride is long and I don't want you sullying your butt with a filthy public restroom." Carla said as they continued walking.

'TRAIN!?' Natsu/Wendy thought incredulously.

What happens now?