Willem en Saskia zitten in een boom, A-A-N H-E-T K-U-S-S-E-N (8)
hmm not as catchy!
In Australia English (can't speak for others), you can sit 'on' a specified part of a tree (e.g. on a branch), but you can only sit 'in' the tree itself
I guess I cannot say about Australia, but in Canada at least, both statement are valid, but they mean different things.
"Sitting in a tree" is where a person sits on say a branch, of a large tree.
"Sitting on a tree" would be where a person sits on a small sapling or other small tree, where they sit on the entire tree, or most of it.
"Sitting in a tree" is a much more common thing to happen, but the other is still possible to express.
I assume that each are both expressible in Dutch as well, "op een tree" would be "on a tree", but I do not know for sure.
No. The discussion above, started by MisterChronos, applies to Dutch as well as English.