Lol, I actually did that a few times when I was a child and had to go to weekly confessions in parochial school!

I felt like I *had *to say something really bad to make it count, so I’d start with the usual “I had a fight with my sister, I told my Mom I brushed my teeth when I didn’t, etc. etc.”. There would be a long, uncomfortable pause (like the priest was waiting for me to keep going) so then I’d blurt out something like “I gave someone the middle finger yesterday!” when I would never have done such a thing
…Now that I think of it, in the years since I don’t believe I ever confessed to previously lying to a priest in confession.