I've tried and failed many times, but there was this one time if thought I felt a few feathers, but they were gone by the time i checked
I used to go around looking for yeerk pool entrances too, this one time i was at the hockey rink and i noticed that there was no locker room 13, it went from 12 to 14 and im like wtf, so i start looking everywhere for it thinking secret yeerk entrance! asked a few people, no one would give me a straight answer, f-in yeerks. 10 years later I got a job at that hockey rink, still havent found the yeerk pool tho (haha seriously i work there)
Oh and once as a kid I jumped off the bunk bed trying to fly and I hit the floor HARD lol did not even fly a little bit