Ask many a grade-schooler (and many an adult, for that matter) what animal the korban pesach is, and he'll tell you "a sheep".
Do we have some tradition (or historical evidence) that it was usually a sheep? If not, how did it happen that people associate the korban with a sheep?
 I have no empirical evidence to offer as far as asking people: it's just my impression. But all I can find using Google (that discusses the pesach as a goat without mentioning that it can be a sheep) is discussing individual cases in which someone brought a goat (including, of course, the case in parashas Tol'dos), plus one blog post. On the other hand, there is much mention of the pesach as a sheep without mentioning that it can be a goat; see e.g. a
vbm-torah.org article and a