A Piraro pun, on flash (with an accompanying play on card, as in playing card and flash card).
I’ll start with flash in the compound flash card. From OED2 on the compound; a definition is provided in the 1945 quote:
1923 Cumulative Book Index Apr. 18 Flash cards for rapid word drills.
1945 C. V. Good Dict. Educ. 173/2 Flash card, a small card of heavy cardboard having on it written or printed letters, words, phrases, numerals, or combinations of numerals for computation; used as an aid to learning, the teacher holding each card up for the class to see for a brief interval.
1953 W. A. Wittich & C. F. Schuller Audio-visual Materials iii. 53 Flash cards..ultimately create relationships and understandings of the symbols and the objects for which these symbols stand.
1964 Listener 12 Nov. 775/2 The raising of children’s ‘flash-cards’: what do you think of this?—two seconds to answer.
The OED treats flash card as a N + N compound (the sub-entry is under the noun flash), but I think a V + N analysis (‘card that one flashes’) is more likely. But then the OED treats all compounds with first element flash (flash point, etc.) as having the N flash.
Then there’s the slang verb flash (which is the base for the noun flasher):
trans. (also refl.). slang. Of a man: to exhibit or expose (part of one’s body, esp. the genitals) briefly and indecently. Also intr.
1846 Swell’s Night Guide 119/1 Flash, to sport, to expose, he flashed his root.
1893 J. S. Farmer & W. E. Henley Slang III. 11/2 To flash it,..to expose the person.
1968 [implied in: J. Lock Lady Policeman ii. 11 City parks also have their share of ‘flashing’. [at flashing n.1 5]
1969 M. Pugh Last Place Left xv. 108 He has a great faith in people like me. He would flash himself to the Sovereign before he searched my house.
1978 G. Vidal Kalki iv. 104 Men stared at me. Some leered. None, thank God, flashed.
That takes us to the cartoon world of cards, where flash cards expose themselves to playing cards.