U.S. Courts of Appeals sometimes name district judges or retired appellate judges to sit “by designation” in a three-judge panel. I knew that retired Justices sometimes so serve. BTW, there is no “senior status” for Justices, but their retirement is pretty much the same as for Circuit judges who take senior status.
I don't recall any previous retired SCOTUS judge sticking around to "fill in" as a judge on the federal courts now and then. I know Sandra Day O'Connor taught courses on Constitution Law and the Supreme Court after her retirement, and Harry Blackmun PLAYED a Surpeme Court judge in the movie Amastad (should have played a pro-slavery judge instead of Joseph Story!)
Per Woodward & Bernstein's book The Brethen, William O. Douglas had a major stroke and no condition to serve as a SCOTUS judge, and was basically forced into retirement by his colleagues. But then he discovered that a retired SCOTUS judge was entitled to keep one law clark and maintain chambers at the Supreme Court building and be a non-voting "observer" at Supreme Court cases, as a ceremonial courtesy. So the loon attempted to play pretend Supreme Court Justice almost 2 years into his retirement during the 1976-1977 session. It turned out to be quite an embarrassment to the other 9 justices because he would show up for "work" in robes during the proceedings and pretend to be "hearing" the case, and even have his clerk write up bogus "opinions" that had no legal power and try to circulate them to his former colleagues to read, in an effort to sway their vote.
Finally, they took him aside quietly and told him on no uncertain terms that there was no place for a "tenth justice" on the court.
On a most unrelated topic, TV judge Marilyn Milian had retired Judge Wopner back in one episode to serve as "guest judge". Probably a ratings stunt.