*16+ any shape
Playing in a team match against expert opponents who are capable of psyching, but rarely do (i.e. both are over 40), you come across this strange auction. At the table I decided to trap pass in the hopes the auction wouldn't die and it didn't. It lead to a couple of interesting discussions.
1) Would you start with a trap pass or 2NT (GF in our methods)?
2) What is your fourth call going to be?

Help

P - (P) - 1♣* - (2♠!)
P - (3♠!) - P - (P)
X - (P) - 4♣ - (4♠!)
?