Strange dark green marks on bedding & carpets

[getupgonow]

My 9 year old's bedding (duvet and top sheet, not mattress) and rug have strange, dark green smears on them! We have no idea where they've come from or what they are.

His window was open last night, but we closed it mid morning and didn't notice anything before tonight.

Any clue as to what it could be?? I thought about a bird/animal being trapped in the room but there's no sign of it now if it was.

New green pyjamas? This happened to me with red pj bottoms from Primark.

Pics?

No new green clothes.

Bedding in washing machine & carpet covered in vanish so can't do photos, but smears of dark green 3-4 inches long.

This is the best I can do - the marks on the yellow won't come out yet

Is it like a slug trail? We get slugs on our house but their marks tend to be clear or yellowish and shiny. They haven't made it on to the beds yet (I don't think ).

We had this recently with snail poo, but it didn't look exactly like that. That looks more like a trail of drops.

Does it smell?

Could a green felt tip have accidentally been smeared around?

It doesn't smell at all.
We've previously had slug/snail trails and they didn't look like that.

It won't come out the rug at the moment either.

My OH said it was solid (he said like bits of concrete) before we tried to clean it

Playdoh or something?

Slime!!!

Do they have slime or putty in their room? We had a putty spillage and it looked quite similar.

Hmm - yes, although he's sweating blind he doesn't know where it came from - I'll quiz him in the morning!

If its like concrete it could be snail or slug poo.