While Jazz was at my parent's house on Valentine's weekend she was learning how to get on an off a little kid seat they have (it was my dad's seat when he was a kid, then me & my sister used it until we were about 7, now it's sitting right between mum & dad's chairs at their house for the grandkids.

She learnt to get on, turn around and sit on her bottom, then slide forward to get off (after apparently trying to get off head and hands first a few times). Now she slides off the couch at home nicely and deliberately, she'll go from sitting, turn around and push herself off feet first while she's facing the couch and can hold onto it for support. Matt's seen her climb up the couch (while he was laying on it), but I haven't seen her do that.
I might move her little Dora couch around so it's facing the TV and see if she sits on it - she doesn't normally, but if we put her boyfriend (AKA: Iggle Piggle) on the couch, then she might sit on it.