Lightly spray a 9×13-inch pan with nonstick spray and set aside.
In a large pot over low heat, melt the butter and dissolve the salt.
Add the mini marshmallows and stir until completely melted and smooth. Remove from the heat.
Stir in the vanilla extract. Then fold in the Rice Krispies until evenly coated.
Transfer the mixture to the prepared pan. Use lightly buttered or damp hands to gently press the treats into an even layer. Don’t compact them, or the bars will turn dense.
Let cool for 1 hour, then cut into 16 triangles.
Transfer the frosting to a piping bag and snip off a small corner.
Pipe a small amount of frosting onto the back of two pretzels and press them onto the top corners of each triangle to create the antlers.
Pipe two small dots of frosting and attach the candy eyes.
Pipe a small dot of frosting onto the back of a brown mini M&M and press it onto the tip of the triangle to create the nose. For Rudolph, use a red mini M&M instead.