Nothing special.
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Its called the catastrophic alignment or planetary alignment
Yes. If it is not straight, then it is not a line.
No. Almost never happens. Depends on how well aligned you mean, occasionally all the planets will be within 45° (as seen from the Sun) or within a cone that has the vertex at the Sun and has an opening of 30°, this happens every decade or so. All the planets can never align less than 2° because the deviation from the ecliptic for some of the planets is greater than this.
it just a straight line
If it is not straight, then it is not a line.