The ornamental design for a “happy stethoscope,” as shown and describe.
The sole FIGURE is a front view of a “happy stethoscope” showing my new design.
The broken lines adjacent to the claimed areas represent the bounds of the claimed design; the broken lines form the no part of the clamed design. The design consists of the appearance, arrangement, and relative placement of the pattern shown within the broken lines as illustrated as surface ornamentation on a stethoscope tubing.