Yeah their comment doesn’t seem right to me. After a bit of googling I found this answer talking about heating things up to see relativistic effects, however because the velocities of the atoms in an object that has been heated up are random it’s most likely not possible to detect any relativistic effects. https://physics.stackexchange.com/questions/351773/is-there-a-relation-between-fluctuations-temperature-and-time-dilation
The original meme: https://knowyourmeme.com/memes/giant-thumb-guy
Usually the person on the left is saying something negative that the group enjoys. Then one person of the group gives them a dismissive thumbs up and continues their convo. In OP the joke is that the thumbs up kind of looks like a cello, instead of the normal meme layout instead the guy is simply asking for a cello and the group gives him one.