Spot (and identify if poss) the cuckoo in the nest. Son had planted a
tray of sweetpea seeds; most of them have come up, but one plant looks
totally different to the others. Probably its seed looks pretty much
like a sweetpea's seed (son has lots of difficulties so he would not
notice if it was subtly different , but I am fairly sure he would notice
if the seed had been glaringly different).

http://www.sidtech.co.uk/iu/soup936104423291.JPG