Andrew Johnson was acquitted during his impeachment trial since the Senate fell short of 1 vote (35 out of 36). That's the closest it's ever gotten.

The funniest thing that could possibly happen would be if a long drawn out 25th amendment battle that goes nowhere for months, then Biden resigns out of respect for procedure, then Harris is made president and immediately impeached for...I don't even know, admitting to smoking weed one time