I claim the ornamental design for a plush star belly dog, as shown and described.
FIG. 1 is a front perspective view of a plush star belly dog;
FIG. 2 is a front view of the plush star belly dog of FIG. 1;
FIG. 3 is a rear view of the plush star belly dog of FIG. 1;
FIG. 4 is a left side view of the plush star belly dog of FIG. 1;
FIG. 5 is a right side view of the plush star belly dog of FIG. 1;
FIG. 6 is a top view of the plush star belly dog of FIG. 1; and,
FIG. 7 is a bottom view of the plush star belly dog of FIG. 1.
The broken lines in the drawings illustrate portions of the plush star belly dog that form no part of the claimed design. The dot-dash-dot broken lines in the figures depict boundaries of the claim that form no part thereof.