FQL profile.pic_square и thread.subject

Как говорится в документации

Facebook Query Language, or FQL, enables you to use a SQL-style interface to query the data exposed by the Graph API. It provides for some advanced features not available in the Graph API, including batching multiple queries into a single call.
You can execute FQL queries by fetching https://api.facebook.com/method/fql.query?query=QUERY. You can specify a response format as either XML or JSON with the format query parameter.
Queries are of the form SELECT [fields] FROM [table] WHERE [conditions]. Unlike SQL, the FQL FROM clause can contain only a single table. You can use the IN keyword in SELECT or WHERE clauses to do subqueries, but the subqueries cannot reference variables in the outer query's scope. Your query must also be indexable, meaning that it queries properties that are marked as indexable in the documentation below.
FQL can handle simple math, basic boolean operators, AND or NOT logical operators, and ORDER BY and LIMIT clauses.
For any query that takes a uid, you can pass me() to return the logged-in user. For example:
SELECT name FROM user WHERE uid = me() 
Other functions that are available are now(), strlen(), substr() and strpos().
Here's an example of a subquery that fetches all user information for the active user and friends:
SELECT uid, name, pic_square FROM user WHERE uid = me()
OR uid IN (SELECT uid2 FROM friend WHERE uid1 = me())

Они не упомянули присоединиться. Так что, на мой взгляд, вы не можете этого сделать.