I had done Basic Run Plus a ton of times, obediently following my cat and never getting getting the choice to do another course. I thought my game was broken or something, that couldn't be all it did. Then I decided to follow the other cat that zipped by me. If you can catch the other cat, it takes you on a different path. In future games follow the next cat and it will give you a third course. After you complete a third course, it finally gives you an advanced course. Yeah! That's where I'm at now, I don't know if there is anything beyond that or how to get to it.
If everyone already knew this, I'm sorry for posting old info, but I thought it was kind of fun.

No wonder I never advanced on basic run plus. I knew basic run had extra courses I followed every once in awhile but didn't know it was required to find the new courses to advance difficulty. I hate chasing the dogs or cats. I get too tired running in the first place, but good to know thanks.

Haha! I figured this out the other day. It wasn't until my 6yo son was playing that I saw it. He runs FULL OUT the entire time. He has that crazy 6yo energy level. He runs so fast that his Mii falls down alot, but when the dog goes by it picks up speed and goes on a different course. Funny that it took a spastic 6yo for me to see it!