<label class="clicktogif" title="click to show gif">
  <input type="checkbox">
  <img src="https://media.giphy.com/media/XV74ZvGRXcZdS/source.gif" alt="Captain America saying he can do this all day - animated">
</label>

label.clicktogif {
background: url('data:image/svg+xml;charset=UTF-8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 -256 1792 1792"><path d="M1288.678 637.83q0 37-33 56l-512 288q-14 8-31 8t-32-9q-32-18-32-55v-576q0-37 32-55 31-20 63-1l512 288q33 19 33 56zm128 0q0-104-40.5-198.5t-109.5-163.5q-69-69-163.5-109.5t-198.5-40.5q-104 0-198.5 40.5t-163.5 109.5q-69 69-109.5 163.5t-40.5 198.5q0 104 40.5 198.5t109.5 163.5q69 69 163.5 109.5t198.5 40.5q104 0 198.5-40.5t163.5-109.5q69-69 109.5-163.5t40.5-198.5zm256 0q0 209-103 385.5t-279.5 279.5q-176.5 103-385.5 103t-385.5-103q-176.5-103-279.5-279.5t-103-385.5q0-209 103-385.5t279.5-279.5q176.5-103 385.5-103t385.5 103q176.5 103 279.5 279.5t103 385.5z" fill="LightGrey"/></svg>') DimGrey no-repeat center center;
  display: block;
  float: left;
}
label.clicktogif:hover, label.clicktogif:focus-within  {
background: url('data:image/svg+xml;charset=UTF-8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 -256 1792 1792"><path d="M1288.678 637.83q0 37-33 56l-512 288q-14 8-31 8t-32-9q-32-18-32-55v-576q0-37 32-55 31-20 63-1l512 288q33 19 33 56zm128 0q0-104-40.5-198.5t-109.5-163.5q-69-69-163.5-109.5t-198.5-40.5q-104 0-198.5 40.5t-163.5 109.5q-69 69-109.5 163.5t-40.5 198.5q0 104 40.5 198.5t109.5 163.5q69 69 163.5 109.5t198.5 40.5q104 0 198.5-40.5t163.5-109.5q69-69 109.5-163.5t40.5-198.5zm256 0q0 209-103 385.5t-279.5 279.5q-176.5 103-385.5 103t-385.5-103q-176.5-103-279.5-279.5t-103-385.5q0-209 103-385.5t279.5-279.5q176.5-103 385.5-103t385.5 103q176.5 103 279.5 279.5t103 385.5z" fill="MediumSeaGreen"/></svg>') DarkSlateGrey no-repeat center center;
  display: block;
  float: left;
}

.clicktogif img {display: block;}
.clicktogif input[type=checkbox] {
    position: absolute;
    left: -100vw;
}
.clicktogif input[type=checkbox] + img {
  opacity: 0;
}
.clicktogif input[type=checkbox]:checked + img {
  opacity: 1;
}