Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Series # | Season # | Title | Directed by: | Written by: | Original air date |
| --- | --- | --- | --- | --- | --- |
| 66.0 | 1.0 | "Joey" | Harry Gerstad | David Chantler | February 18, 1956 |
| 67.0 | 2.0 | "The Unlucky Number" | Harry Gerstad | David Chantler | February 25, 1956 |
| 68.0 | 3.0 | "The Big Freeze" | Harry Gerstad | David Chantler | March 3, 1956 |
| 69.0 | 4.0 | "Peril by Sea" | Harry Gerstad | David Chantler | March 10, 1956 |
| 70.0 | 5.0 | "Topsy Turvy" | Harry Gerstad | David Chantler | April 21, 1956 |
| 71.0 | 6.0 | "Jimmy the Kid" | Philip Ford | Leroy H. Zehren | April 28, 1956 |
| 72.0 | 7.0 | "The Girl Who Hired Superman" | Philip Ford | David Chantler | May 5, 1956 |
| 73.0 | 8.0 | "The Wedding of Superman" | Philip Ford | Jackson Gillis | May 12, 1956 |
| 74.0 | 9.0 | "Dagger Island" | Philip Ford | Robert Leslie Bellem | May 19, 1956 |
| 75.0 | 10.0 | "Blackmail" | Harry Gerstad | David Chantler, Oliver Drake | May 26, 1956 |
| 76.0 | 11.0 | "The Deadly Rock" | Harry Gerstad | Jackson Gillis | June 2, 1956 |
| 77.0 | 12.0 | "The Phantom Ring" | Philip Ford | David Chantler | June 9, 1956 |
Question:
What is the airdate when the title is "topsy turvy"?
Answer:
1.0