A male co-worker who is an American citizen entered Canada
with his young daughter; however, his wife was staying at home
in Texas and was fully aware of the trip. His wife's father was
picking them up at the airport.

He was thoroughly reamed out... at one point it was suggested
there was some kiddie porn situation going on as they found
a picture of his daughter in the bathtub on his laptop.

It did not help that another co-worker was travelling with them
who had a DUI conviction in the States on his record.

3 hours later after much questioning, searching and the father
in law vouching for them... they finally left the airport.

Me, on the other hand, being single with no kids as a Canadian
citizen living and working in the United States never have a
problem when returning... other than the "Why are you coming
back question?" which seems rather silly.