I actually had one. I'm about the same age as Watterson, and had a stuffed tiger that was identical to the one in the strip. I have a sneaking suspicion that he did to, since he captures the odd proportions of the original so perfectly. In any case, it adds a whole 'nother level when I read the strip, allowing me to relate to it eerily well. That tiger was threadbare after years of being my constant companion (my mom had to sew the tail back on several times).