I was a big fan of the Turtles when I was a kid, but I got most of that info by looking it up in an episode guide. The Internet is a wonderful thing. 😉
That was the only time April was tickled on the show. Other characters were tickled at various points, but to my recollection they were all male (except for one girl who you didn't actually see being tickled, though you did see her laugh).
I guess either the DVDs somehow number them differently, or they changed the order or made a mistake, or something. I take your word for it that that's what the DVD says, but I'm just sayin', all the info I can find says 3.